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By C. E. Seaman, H. Jiang, S. Klima, T. W. Beck, Y. Zheng

Respirable coal dust has been long recognized as a leading cause of multiple lung diseases. Efforts aimed at reducing dust concentration in underground mines have been made, but increases in coal workers’ pneumoconiosis incidence rates over the last 20 years among U.S. miners are concerning. Dust deposition and water spray suppression are two types of dust removal mechanisms in underground mining activities. In this study, laboratory tests were conducted to investigate the respirable dust decay characteristics during deposition and suppression processes in a confined dust chamber. Dust concentration and size distribution were monitored continuously throughout each 60-minute test. A number-basis particle size distribution was used for analysis to capture the changes of smaller size fractions within the investigated dust sample. This study found that around 62.1% of respirable dust particles were deposited at the end of the deposition test. In addition, the final deposition rate for very fine particles can be less than 20%. The results from the suppression test indicate that larger particles were removed quickly; however, sub-micron particles remain suspended through the 60- minute water spray, and particles under 0.5 µm can be considered irremovable dust under single-spray operation conditions. This study also observed the resuspension of a significant amount of sub-micron particles by the water spray. The results of this study provide basic information for improving dust control strategies and can be utilized to improve the water spray performance for reducing airborne dust levels.

Mar 2, 2022

By Jian Liu

The dissolubility of a natural sphalerite (ZnS) in the entire pH range was theoretically calculated, and its practical dissolution in an aqueous solution at different pH values in an inert environment, together with its surface properties after dissolution, was fully investigated. The results of the investigation indicate that the total concentration of Zn (CZnT) decreases significantly with the increase of pH value, while the pH value is set below 8; however, it reverses when the pH value reaches 8. Such a tendency is similar to that of the theoretical calculations, although the experimental CZnT were much higher than those of the theoretical calculations. The X-ray photoelectron spectroscopy (XPS) of the sphalerite surface after its dissolution under alkaline solution shows that a polysulfide (Sn 2-) surface layer with a binding energy (BE) value of 162.96-163.25 eV is present on the surface, and the percentage of Sn 2- increases significantly with an increase in pH value; the undissolved and dissolved sphalerites under the acidic solution have a negligible difference in S2p peaks. The surface S/Zn ratio of all dissolved sphalerites shows a marked Zn enrichment and S deficiency. An atomic force microscope (AFM) view of the sphalerite surface, after its dissolution under the alkaline solution at a pH of 12, shows that the surface is significantly different in morphology from that of the undissolved one.

May 1, 2012

By J. M. Wempen

Booster fans in underground coal mines are often located using the concept of a neutral point. Normally, intake airways are maintained at higher absolute pressure than return airways; therefore, air leaks from intake to return. By adding a significant pressure force to a region of a ventilation system, booster fans installed in a return airway can increase the pressure in the return so that air leaks from return to intake. This is commonly referred to as recirculation. The neutral point occurs at the location in the system where the pressure difference between [ ] the intake and the return airway is zero. At this point, there is no leakage or recirculation. Ideally, placing a booster fan near the neutral point minimizes leakage and recirculation. However, in practice, the position of the neutral point is not static and it changes as the ventilation system parameters change. Booster fans have the potential to increase the capacity and efficiency of coal mine ventilation systems. However, these fans add a significant pressure source to ventilation systems and can create areas where the pressure in the intake is less than the pressure in the return causing recirculation. In systems with multiple booster fans, there may be multiple recirculation paths and, as the capacity of these fans increases, recirculation is more likely to occur.

Jan 1, 2012

By Henry T. Mulryan

The philosophy, strategy and techniques of successful marketing of talc, differ sharply from those applied to most other mined products. Unlike non-ferrous metals, there are no commodity exchanges to facilitate the transfer of goods. Unlike iron ore and some non-metallics, assured markets by means of long term contracts are practically non-existent. Talc must be sold and sold and sold again. The normal channels of talc distribution are almost identical to those used, by the chemical industry. These consist of a blend of producer marketing staff, field technical service, and sales force; and independent chemical wholesalers. Like the term "chemicals", there is tremendous product diversity contained in the rather loose expression "commercial talc". Certain kinds of talc, processed in conventional ways, are regarded as commodities by the consumer. That is, that material from one source or supplier is considered to be effectively interchangeable with those available from a number of other areas and producers. Under such conditions, lowest delivered price, quickest delivery, and best, customer service, are the key factors in a successful sales effort.

Jan 1, 1965

By J. A. Lombardi

Innovative hard rock narrow-vein, longwall, and stope leach mining systems concepts are described and evaluated economically. The principal tool proposed for use in these systems for both mine development and production is the U.S. Bureau of Mines radial-axial splitter. The mining systems concepts are prefeasibility level costed and projected to be cost competitive for steeply dipping veins, 0.6-1.2 m wide, for horizontal tabular ores 2 m -5 m thick, and for leachable ores with greater than a 1.7:1 stripping ratio. In all of the systems the orebody, less swell, is retained underground for use as backfill.

Jan 1, 1994

By G. A. Shirey

Breakthroughs in software technology and in computer hardware capabilities have opened new opportunities to develop more accurate process simulators and to reduce the operating time to reasonable levels. As a result, there are several new simulation packages being commercialized for modeling coal preparation plants and pulverized coal-fired power plants, and the users of these packages are reporting significant improvements in process efficiency and operating costs by implementing the simulators' results. This paper provides an overview of some of the models currently in use at CQ Inc., including the ASPEN PLUS"" Coal Cleaning Simulator, the Ultramax® process optimization software package, and EPRI's Coal Quality Impact Model?. Case histories of specific applications are also presented.

Jan 1, 1995

By W. O. Henderson, H. W. Seaney

The sinking and grouting methods employed at the 3C and 3D ore hoisting shafts and the No. 5 service shaft are discussed. The reasons for selecting a circular section over a rectangular one and other technical aspects are reviewed.

Jan 1, 1974

By S. E. Phillipson, S. Romberger

The Late Miocene San Cristobal Ag-Zn-Pb deposit represents syngenetic and epigenetic mineralization with low- and high-sulfidation characteristics. The geology of the deposit is characterized by barren dacitic ring fracture domes, mineralized resurgent rhyodacite domes, strongly altered and mineralized tuffaceous lacustrine sedimentary rocks and an extensive crystal-lithic tuff debris apron. The orebody is hosted by intracauldron sedimentary rocks and breccias. Fluid inclusion data suggest that silver, lead and zinc were transported as chloride complexes and precipitated by cooling in veins from <5% (by weight) NaCl eq. fluids at 170° to 215°C. Silver spatially and perhaps temporally associated with resurgent rhyodacite was transported as a chloride complex and precipitated by increased H2S activity or increased fluid pH.

Jan 1, 2002

By Martin Valeri

The operation described in-this paper will be confined to the Nemacolin Mine of The Buckeye Coal company, Nemacolin, Pennsylvania.&apos; This mine is-located on the Monongahela River approximately sixty miles south of Pittsburgh. The mining is in the Pittsburgh seam that has an average thickness of 88 to 90 inches. The current practice is to mine approximately 80 inches, leaving 8 to 10 inches of roof coal. All of the coal produced is used solely for by-product coking by the parent Youngstown Sheet & Tube Company, Youngstown, Ohio. Eight to ten inches of top coal are left by the miners to prevent air slacking of the draw slate. In addition, this top coal which will float at the washing gravity has a very high ash and sulphur content, and when mined, seriously affects the quality of the clean coal product.

Jan 1, 1961

By William H. Dresher

A study has been made of the reaction mechanisms occurring during the salt-roast process to form water-soluble sodium vanadate compounds from the vanadium oxide compounds present in vanadium-bearing ores and concentrates. Two reactions have been identified, either of which lead to water-soluble compounds--oxidation of sodium chloride by water vapor and. oxidation of sodium chloride by oxygen. The former reaction has been found to be predominant in the salt-roast process. A kinetic treatment of the data has shown that for the formation of sodium metavanadate the rate-controlling step in the reaction, in which sodium chloride is oxidized by water vapor is the decomposition of a species containing water and sodiumm chloride, on the surface at the gas-solid interface. For the formation of sodium pyrovanadate, the rate-controlling step is the decomposition of a species containing water and sodium metavaradate on the surface. The transportation of water through the system, perhaps as a sodium chloride-water complex or a sodium metavanadate-water complex, and the actual chemical reaction are relatively fast compared to the initial surface decomposition step. A similar treatment on the data for the oxidation, of sodium chloride by oxygen has shown that the rate-controlling step, is the actual transportation of oxygen from the gas-solid interface to the reactive site. This transportation is by a sequence of two diffusion processes. Transportation during the early stages of the reaction is by the diffusion of oxygen through a continuous layer of reaction product. After, the first few minutes of reaction time a second diffusion process begins and is continuous for the remainder of the reaction. This second diffusion process involves the diffusion of oxygen, through a layer of reaction product that has developed voids around which the oxygen must diffuse. The hindering, nature of this latter process causes the rate of transportation of oxygen to the reaction site to be considerably slower than by the simple diffusion mechanism initially followed. A thermodynamic treatment of the data has shown that the energy of activation for the decomposition of the water-sodium chloride species on the surface is -12.1 Kcal. per mole. For the decomposition of the water-sodium metavanadate species on the surface&apos; the energy of activation is -15.1 Kcal. per mole. The results of this study indicate the limiting mechanisms of the basic reactions occurring during the salt-roast process. These results suggest what variables should be examined in applying this information to actual plant operations.

Jan 1, 1961

The results of studies to ameliorate acid mine drainage by retarding the rate of oxidation of pyrite at source are discussed. In the transpassive region, pyrite oxidizes by reactive dissolution, mass transfer through the product layer and diffusion in the bulk solution. One can decrease the rate of pyrite oxidation by inhibiting either oxidation reactions or cathodic reactions. It is demonstrated in this study that some surface active reagents extend the passive region by affecting both the anodic and cathodic processes. The extension to higher potentials occurs by inhibition of the anodic dissolution process whereas to lower cathodic potentials through decrease in the rate of reduction of molecular oxygen and/or ferric ions. To retard the oxidation of pyrite by ferric ions, which is considered to be the dominant oxidant under conditions of acid mine drainage, it would be necessary to restrict mass transfer or promote complexation of ferric ions at the surface. Imidazoline based reagents were found to be most effective in meeting this goal.

Jan 1, 1994

By D. T. Iseley, A. L. Atta-alla

INTRODUCTION The extension project of the East Line Subway of Atlanta&apos;s subway network includes the construction of two single track transit tunnels under Interstate Highway 285. The project will be in DeKalb County, Georgia. The length, width, and height of each tunnel are 54.25, 6.3, and 7.2 m (178, 21, and 23 ft) respectively. The ground cover above the tunnel crown ranges from 1.5 to 3.25 m (5 to 11 ft). A soil pillar about 5.5 m (18 ft) wide will remain between the tunnels. The construction of each tunnel includes (i) installation of 21 steel soil support pipes of 75 cm (30 in) diameter, (ii) jet grouting 15 soil cement shafts of 60 cm (24 in) diameter in the soil under the pipes, (iii) contact grouting behind the tunnel lining and between soil support pipes and pavement, (iv) excavation of soil inside the soil support arch, and (v) installation of steel pile foundation, steel sets, and permanent tunnel lining of cast-in-place concrete, all as shown on the cross section in Fig. 1. The soil profile can be described from top to bottom as cement/asphalt concrete pavement, a fill layer consisting mostly of stiff sandy silt/firm silty sand, a residual soil layer consisting mostly of silty sand/sandy silt, partially weathered rock, and solid rock.

Jan 1, 1991

By A. F. Ogg

The installed world steel capacity remains 20% above the present world steel demand. Energy costs have risen enormously in recent years, as illustrated in Figures 1 and 2. The role of the sinter plant is becoming more exacting as it becomes vital to minimize energy consumption. Continuous grate sintering, although pioneered in the United States, has always been the second grade burden preparation route, due to the predominance of easily up- graded ores which were more readily agglomerated by pelletizing. To achieve blast furnace performance up to best world standards, sinter of consistent high quality must be produced with virtually no atmospheric pollution. The plants must be capable of achieving this demanding level of quality whilst utilizing high proportions of revert materials, iron ore concentrates and fluxes . However, with the present difficult economic climate in the iron and steel industry, the economic production of sinter and ultimately steel is becoming increasingly important. The iron and steel industry is looking closely at costs and is identifying the need for sinter plants that will cope with a wide range of sintering materials to give the cheapest blend at varying output levels dependent upon demand. In order to meet these requirements, sinter plant builders are designing plants with particular attention on flexibility.

Jan 1, 1980

By M. J. Klishis

This paper presents the findings of a study on roof bolters&apos; hazard exposure. A "micro-analysis" of accident data was combined with ergonomic observations of roof bolter operators to categorize bolting-related injuries and a checklist was constructed. Bolting-related problems were identified as situations that could expose bolter operators to hazards. Approaches to avoid these situations were applied at six mining operations to evaluate specific problems in roof bolting operations. The re-search emphasized the importance of analyzing worker behaviors in the context of mining situations and equipment design problems that lead to human error accidents.

Jan 1, 1995

By Willard A. Murray

Investigations of underground coal gasification (UCG) have been actively pursued by the U.S. Department of Energy since the early 1970s; the Lawrence Livermore National Laboratory (LLNL) conducted its first field experiment in 1976. In conjunction with field and laboratory studies of the process of recovering energy in the form of combustible gases from the burning of coal deposits in situ, an extensive environmental program has been conducted at LLNL under the auspices of both the U.S Department of Energy and the U.S. Environmental Protection Agency. This program has focused on groundwater contamination and ground surface subsidence caused by UCG. The material presented in this paper is a summary of results from the environmental studies of UCG activities conducted by LLNL as described by Mead, et al. (1981) and supplemented by the author&apos;s experience with this program in 1980 and 1981. The following sections describe specific groundwater contamination and surf ace subsidence problems encountered during field experiments in northeastern Wyoming, and will discuss implications of preliminary findings from geohydrological investigations of a site in southwestern Washington. Finally, possible environmental control technologies that are most likely to be effective in mitigating environmental impacts are discussed.

Jan 1, 1982

By Frank H. Madison

The percentage depletion deduction on Federal Income Tax Returns under the provisions of the 1939 Internal Revenue Code and of Sections 611 to Section 615, inclusive, of the revenue act of 1954, have created innumerable administrative difficulties, and a new interpretation of "gross income from the property" in that the Courts have expanded the ideas of what constitutes "gross income from the property" to a degree unheard of and unthought of prior to the enactment of these two codes. Originally, under the Revenue Acts of 1917, 1918, and 1920 depletion was allowable, based upon mine valuations as of March 1, 1913; if the mine was owned prior to March 1, 1913; upon cost, as of the date of acquisition if purchased subsequent to March 1, 1913; and upon a "discovery" basis if the mine was discovered after March 1, 1913, The "jab" for mine valuations as of March 1, 1913 and for discovery valuations and depletion was not as bad as it has been made out to be. Thousands of valuations and estimates of reserves were made and agreed upon between taxpayers and Internal Revenue Service engineers and as the years went on the answers have been found to be "reasonable." However, human nature being what it is each case was a battle of wits - of a sort - and many resulted in severe differences of opinion and litigation. As tax rates increased the situation was not bettered. I could talk for several hours on this phase of depletion but it is all past now andwould not give any real service or better understanding of the matter.

Jan 1, 1958

By Roland Hoet

Mine operators, conveyor system designers, consultants, and manufacturers have had opportunities over the past decade to utilize various actively controlled technologies to drive complex underground conveyor systems. These technologies included several electrical drive solutions, mechanical drive solutions, and hydromechanical (fluid coupling) drive solutions. All of these technologies have their inherent advantages and disadvantages, and only after several years of operation can mine operators fairly evaluate the overall benefits (short term performance and cost vs. longer term operational and maintenance costs) of any particular drive. Far too often in today&apos;s world, decisions for new equipment are made with inadequate regard to issues concerning serviceability and maintainability. Many of the newer electrical technologies (primarily AC variable speed drives) which have been used in recent years were selected based on the perceived desirable benefit from variable speed operation. This technology, however, which differs sign8cantly between various manufacturers, is in a constant state of evolution which puts into question the manufacturers&apos; ability for long-term product support. In addition, various forms of this technology have also generated some undesirable operational issues, including reduced motor life, harmonics for the power system, and mine communications problems. This technology is also extremely current-limited, which results in problems handling overload conditions, a frequent occurrence often resulting from a decline in the coal recovery rate (conveying more rock than coal). The fluid coupling, however, is based on a technology which has been used successfully in underground conveyor applications for decades. Although the base hydrodynamic technology is well proven and has inherently beneficial characteristics on conveyor applications, Voith has continuously improved on this technology to meet the increasing demands of today&apos;s challenging conveyor haulage systems. Recognizing a need in the market for a reliable, actively controlled drive system, Voith Turbo began development in 1996 of a new, actively controlled coupling which was targeted specifically for the higher powered, complex underground conveyors. Voith introduced the new TPKL Fill Controlled coupling product to the market in 1997, and the first two applications for this new technology were on multiple drive mpper booster applications on longwall panel conveyors. Since the successful startup of these two conveyor systems in 1998, Voith has supplied over 200 TPKL couplings to the mining industry worldwide, with over 150 in US coal mining applications alone. This paper will provide an overview of the TPKL&apos;s capabilities, performance, and reliability based on the TPKL&apos;s impressive installation base and operational history.

Jan 1, 2004

By Libby R. Ricafort, Nonato S. Retardo, Jose B. Anievas

This paper shows the metallurgical test results that led to the design of the heap leach facilities of Philex Mining Corporation. The design incorporates a water management model as process solution circulation is excessive with high rainfall intensity in the area. This poses problems in the operations requiring stringent controls than would be necessary in a less severe environment. The corporate perspective embraces on environmentally-sound mineral development. A budget is always provided to environmental management making certain that no industrial development is moved forward at the expense of the environment.

Jan 1, 1996

By X. Song, Q. Zhang

"The development of fracture zones in surrounding rock mass has significant impact on the stability of underground mine roadways. Detection of the fracture zones is of compelling importance for maintaining roadway stability as well as for safe and speedy excavation of the roadways. This paper presents a study conducted at Dong Bao Wei underground coal mine, where the roadways were developed in diabase rock mass. The roadways suffered severe damages, including sloughing and excessive floor heaving. The borehole imaging technique was applied in the study to observe and detect fracture zone development surrounding the roadway openings. Based on the borehole imaging studies, new roadway support systems were proposed to improve the stability. INTRODUCTION At the Dong Bao Wei Coal Mine three main roadways of the west wing were excavated. The three roadways had semicircle arch cross sections and were at a depth of 650 meters, each being about 750 meters in length. The roadways were driven through a section of thick diabase intrusion, which was softened by water with reduced strength and may turn into powder form under weathering. Site investigation indicated that the roadways in diabase intrusion zone were badly damaged due to severe deformation, and very serious roadway sidewall sloughing and spalling accompanied by severe floor heave often occurred.(Figures 1 and 2) In order to ensure the normal use of the roadway, undercuts were excavated. However, this operation seriously affected the roadway construction progress and increased the amount of roadway support operations as well as the roadway maintenance costs. Furthermore, a roof fall accident occurred in nearby drilling site. The investigation indicated insufficient support provided for the roadways which imposed significant safety hazards and would have serious impact to mining production and subsequent mining activities.The support of the main roadways is a critical task and is the focus of the underground opening excavation work at the mine, since more than 40 years of service life is required from these main roadways. For these roadways, large cross sections with high degree of stability and minimal amount of deformation should be maintained. Therefore, providing sufficient and appropriate roadway supports is of significant importance to the coal mine. In this paper, in order to optimize the roadway supporting system, studies were carried out on the geological structures, lithological characters, roof bolt anchoring features and suitable anchoring layers. The studies were aimed at ensuring the stability of mine roadways, reducing the roadway maintenance costs and providing a safe mine passageway for orderly production and progressive development of the mine"

Jan 1, 2016

By M. Li, J. D. Miller

Many technology problems must be solved if we are to continue to produce phosphate at our current rate of consumption. The U.S. produces at least 25% of the world&apos;s phosphate, 40 million tons of phosphate rock per annum with most of the production coming from Florida. Of particular concern are improved separation efficiency and the ability to treat new dolomitic resources. Phosphate flotation technology needs include: 1. Simplification of the standard flowsheet 2. Improved recovery of coarse phosphate 3. Selective flotation for phosphate recovery from dolomitic resources Preliminary results, including tests on plant feed from Florida show that these objectives may be achieved with a new collector chemistry depending on the specific circumstances. The effectiveness of the new collector chemistry has been demonstrated by the preliminary results from single stage flotation experiments both at the University of Utah laboratories and at Florida Institute of Phosphate Research (FIPR) laboratories. In the best case, from these experiments with low grade (5% P2O5) coarse feed (16x35 mesh), a single stage phosphate recovery of 95 % was achieved with a concentrate grade of 31 % P2O5. Such a separation efficiency could not be achieved using the traditional fatty acid/fuel oil collector. Based on these results it seems that a one step process may be possible for phosphate flotation and a research program is justified for the development of this new flotation strategy.

Jan 1, 2001