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By L. Frost

"Since the late 1990s, increased prevalence of severe lung disease among US coal miners has been observed, particularly in central Appalachia where thin-seam mining is prevalent. While respirable silica exposures have been implicated in many cases, the available dust monitoring data from mines shows no explanatory trends. One possible factor could be differences in the relative toxicity of silica particles based on their surface condition. Previous research has indicated that particles with occluded surfaces (e.g., by a thin layer of clay) may be less toxic than those with non-occluded surfaces. However, this dust characteristic has not been investigated before now in central Appalachian mines. In the present study, 18 respirable dust samples from seven central Appalachian mines and two northern Appalachian mines were analyzed to assess the relative occurrence of surface-occluded silica. Results showed that the dust from central Appalachian mines actually had higher fractions of occluded silica, which may be due to extraction of large amounts of rock strata along with the coal. However, the central Appalachian mines also more silica particles overall (i.e., occluded + non-occluded) in terms of total number percentage of respirable particles.INTRODUCTIONResurgence of occupational lung disease among US coal miners, especially in the central Appalachian region, has been observed since the late 1990’s (Gibson, 2016; Zosky et al., 2016; Suarthana et al., 2011; Gamble et al., 2011; Antao et al., 2005; Attfield & Sexias, 1995). In addition to increased prevalence of simple Coal Workers’ Pneumoconiosis (CWP, or “black lung”), the prevalence of severe and rapidly progressive disease has risen dramatically (Almberg et al., 2018; Blackley et al., 2018a, 2018b, 2016, 2014; Graber et al., 2017; Cohen et al., 2016). While exposures to respirable silica have long been known to cause or play a role in diseases such as silicosis or progressive massive fibrosis (PMF), which is conventionally considered as the most advanced form of CWP, it is unclear whether silica is the only culprit in the recent outbreak of severe disease. Indeed, as disease rates have risen, both total respirable dust and silica concentrations generally appear to have declined since the late 1980s, based on regulatory monitoring data in the most affected mining districts (i.e., MSHA coal Districts 4, 5 and 12, which cover central WV, eastern KY and southwestern VA, and southern WV, respectively) (Figure 1). Of course, the latency of disease can vary and may be or more 10 years, but many of the most recent cases are likely to have resulted from exposures that occurred since the late 1980s."

Jan 1, 2019

By S. H. Penn

One of the more challenging aspects of the unfolding age of space travel centers about the opportunity for man to use the natural resources of other worlds. The first of the extraterrestrial worlds to be exploited will be the moon. After only a scant few thousand years of scratching the earth's crust, man will embark upon a venture that for centuries has excited the imagination of many (while staggering that of most) and may become a reality within the next decade. There has never been a time when so much money and effort will have been expended to exploit an area about which so little is known. Paradoxically, this effort combines much of the detached objectivity so typical of our analytical time with the proverbial optimism of the indefatigable prospector. As the earliest manned lunar missions will be brief and exploratory in nature, astronauts will not be expected to attempt to exploit any of the possible lunar natural resources. In later missions, with a more extended period of time available for the astronauts to stay on the moon, it may be desirable or even necessary to "live off the land". The resulting exploitation of lunar resources will be intended primarily to reduce the dependence of manned missions upon terrestrial logistic support and to reduce the cost of maintaining lunar bases.

Jan 3, 1966

By Spottiswood DJ, Kelly EG, Bull WR

An empirical model of a 254mm water-only cyclone treating minus 17001im coal has been developed. The model includes the prediction of by-passing, SG50 corrected, water split and the use of a single equation forthe reduced performance curve of particles in the range 1700-106pm. Particles finer than 106pm did not separate according to specific gravity. Simulations using the model showed the water-only cyclone performance to be dependent more upon feed size distribution than washability when the feed contains high-ash fines, but that, with a deslimed feed, the yield and ash content of the over-flow should be controllable by altering feed rate or feed pulp density.

Jan 1, 1985

By R. R. Klimpel

In this first report, we present a preliminary model based on the simple binary sys¬tem of component B occluded in a matrix of compo¬nent A, for the case where fracture planes can pass with equal ease through A or B. By assuming that the volume fraction of B in AB in the overall matrix is small, which is realistic for many prac¬tical systems, the problem is reduced to a one-¬dimensional treatment which is conceptually easy to understand. The model was programmed for Monte Carlo simulation, and an analytical solution also developed based on the assumption of zero or one mineral fragment per particle. Preliminary ex¬perimental confirmation using a synthetic "mineral¬-host matrix" of known amount and size of B in AB is presented.

Jan 1, 1983

By A. C. Hawken, L. M. Strah

"The Report outlines the Conversion to Rubber Mill Liners and steel grinding balls from the old style Cobalt pocket liners and flint pebbles which had been used in 5'x22' Fraser-Chalmers tube mills for over fifty years. An outline of the past history and some of the plant modifications are mentioned as well.The details pertaining to considerations, modifications and repairs carried out on the mills are described. Factors influencing the rubber liner design are outlined along with the description of the rubber liner design.The performance and advantages to date are given and concludes with brief summary.HISTORYThe original amalgamation-cyanidation mill of Dome Mines Limited went into operation in 1912. Milling has been continuous since 1912, except for two periods; one of 17 months commencing in December 1917, and the other of about 12 months, when fire destroyed the plant in November 1929. Initially the capacity of the mill was 350 tons a day. In 1916 it was raised to 750 tons a day, following which there was a gradual expansion to 1,500 tons a day."

Jan 1, 1977

By Richard B. Moore

This bulletin presents a summary of available information regarding the sources of uranium, radium, and vanadium, the methods used in treating the ores, and the uses of the finished products. In particular the paper describes the ores found in the United States, giving especial attention to those characteristics of the ores and the conditions of their occurrence that affect mining and treatment. ACKNOWLEDGMENTS. In the preparation of this bulletin a number of persons rendered assistance by furnishing information and by making it possible for us to visit the carnotite deposits in western Colorado and eastern Utah at a time of the year when without this assistance it would have been difficult to obtain satisfactory results. We desire to express our thanks to the following persons: Henry Hall, W. L. Cummings, T. V. Curran, K. D. Hequembourg, David Taylor, H. C. Brown, Forbes Rickard, George W. Alsdorf, Dr. Herman Fleck, Orr J. Adams, C. S. Cherrington, Newt. Stewart, O. B. Willmarth, Angus Cameron, George A. Head, and Lorimer Bros.

Jan 1, 1913

By B. Li

"The spontaneous combustion of coal storage pile(Gangue Hill) is one of the seriously threat encountered in coal mining and storage. The dynamic accumulation of internal heat in coal storage pile(Gangue Hill) provides continuous heat-source for coal spontaneous combustion. Combined with the features and characteristics of coal pile storage, a technology of heat pipe(HP) is applied to enhance heat transfer. In order to prevent spontaneous combustion of coal storage piles (hillock) due to regeneration, a method using heat pipes to destroy the heat preservation conditions of coal storage pile(Gangue Hill) is proposed, which reduces the risk of coal spontaneous combustion and prevents coal fire. A theoretical model of Coal-Thermosyphon has set up to analysis the radius of cooling effect area quantitatively. An experimental equipment of the heat transferring in a set of heat pipe, which used to study the influence on coal pile temperature distribution, has been designed. Results show, the heat pipe has a significant effect on inhibiting the coal spontaneous combustion process by destroy the heat preservation conditions of the coal. Under the experimental conditions, the most obvious coal temperature decline appears at radius 20.0mm around the pipe, dropped from 45.8? to 32.5?, a decline of 29%; the coal pile temperature at radius 420mm from 12.9? to 12.4?, a decline of 3.87%. And the research offers an effective and new approach in its application and promotion for preventing and controlling in coal spontaneous combustion.INTRODUCTION China is one of a few countries which utilize coal as the major source of energy in the world, and is the one whose characteristic of energy structure is rich coal, deficient oil and lean gas. Relatively speaking, China is abundance in mineral resources. The coal, which is the fundamental resource in the process of industrialization, is the main energy in china. Thus China cannot alter the situation of coal consumption dominated a leading role in its energy structure in near term.A massive of coal gangue would be produced every year in China with the mining activities. And it’s estimated that almost 360 million tons gangue were dumped in 2003, accounting for 10 percent of the whole coal production. Huge numbers of coal waste piles have more than 2,600 seats, which cover an area of over 12,000 hectares. Worse more, the coal gangue still has an annual growth rate of 100 million tons. Toxic smokes and greenhouse gases are discharged directly and prolongly into the atmosphere due to coal gangue spontaneous combustion. Even worse, waste dump explosion cause massive losses and are able to endanger the safety of workers. For example, one waste dump of the NO.4 Mine of Pingdingshan Coal Group Co., Ltd. occurred twice of explosions in 2005, and about 3.13 million tons of waste rocks were thrown within the range from 100 to 300 meters, eight people were killed and 122 rescuers and miners were burned, and economic losses were estimated more than 3,000 million."

Jan 1, 2015

By Sidi Deng, Sharon Pedraza, Aaron Noble, Subodh Das, Bin Ji, Wencai Zhang, Michael Van Brunt

In this study, a MSWI bottom ash sample was assessed to evaluate the feasibility of various physical beneficiation processes in concentrating valuable elements prior to chemical leaching. The raw sample was initially assayed to determine the content and economic value of various metals present in the material. The potential recoverable value (PRV) of the sample was calculated, and the result showed that the total PRV of the sample was 483 $/ton, with Ti, Sc, Fe, Cu, and Zn being the most valuable metals. Next, various physical separation processes, including size fractionation, froth flotation, magnetic separation, and gravity separation, were conducted to determine the extent to which the valuable elements can be concentrated. The results were compiled into an element-by-beneficiation enrichment ratio (er) matrix that was used to develop suitable beneficiation flowsheets for further consideration. The result clearly show delineation of four products, including a Fe-rich product that can be isolated by magnetic separation (er = 5.0), a Cu/Zn-rich product that can be isolated by flotation (er = 5.3 to 9.4), a Sc-rich product that can be isolated by gravity separation (er = 0.6), and a Ti–rich product that is produced in the residue. Lastly, the leachability of valuable elements from the bottom ash sample was determined by acid leaching tests. The results indicated that it is viable to employ hydrometallurgical methods to recover and purify the valuable metals. This work provides a reference for the recovery of valuable metals from MSWI bottom ash from both the technical and economic aspects.

Apr 27, 2024

By R. C. Dunne, C. T. O'Connor

Flotation practice on eighteen South African flotation plants is described. The plants are categorized as those treating reclaimed tailings, those treating material which has already been subjected to cyanidation or uranium leaching, and those treating milled ore. The similarities and differences are highlighted.

Jan 1, 1998

By Edward H. Eisenbrey

This paper is primarily concerned with the exploration for massive sulphide orebodies. In a discussion of this type, it seems appropriate to establish a few definitions so that all parties may consider the same beast and its habitat. First, the term "massive sulphides", as used here, not only denotes a body of mineralized rock containing in excess of 50% sulphides by volume, but a mass of sulphides that respond as a conductor to the electromagnetic (EM) systems currently in use in exploration. "Disseminated sulphides" refer to all of those sulphide occurrences that respond to the Induced Polarization (IP) geophysical methods most commonly in use in porphyry copper exploration. This latter definition may also include the disseminated sulphide halos so frequently found associated with massive mineralization as well as banded and stringer sulphide mineralization. It is plain to see that these two end members of our definitions can easily blend into each other. The term "volcanogenic" refers here to any and all geologic processes that have their origin in volcanic activity. Thus we are concerned here with the exploration for massive sulphide ore deposits derived from and affected by contemporaneous and post mineral volcanic activity. Furthermore, most massive sulphide deposits are apparently formed in a submarine environment, deposited with extrusive rocks and sediments and/or chemical hot spring accumulations, then enclosed and protected by the addition of more volcanic and sedimentary material then, probably folded and deformed into one of their myriad of shapes.

Jan 1, 1973

By Xia Guangxiang, R. Y. Wan, Yang Hanlin, M. C. Fuerstenau

The mechanism and kinetics of pretreatment on pyritic gold concentrate with the catalytic oxidation acid leach (COAL) process were studied in the temperature range of 80-100°C and oxygen pressure range of 230-1013 kPa, with sodium lignosulfonate (SL) and mixed medium of sulfuric acid (11 g/[ ]) and nitric acid (5.5 g/ [ ]). The results show that nitric acid acts as a catalyst, the surfactant changes the hydro-phobicity of resulting elemental sulfur to favor the oxidation of pyrite, and the oxidation-determining step would be the chemical reaction between nitric acid and pyrite. When about 80% of pyrite contained in the concentrate is oxidized, the gold cyanidation extraction exceeds 95 % . The nitric acid in solution can be recycled and used again.

Jan 1, 1993

By W. T. Gorton

Bonds are required by state and federal law to address reclamation when the permittee defaults. Under various principles of law, a bonding company may propose to perform the obligations of the permittee, however, the negotiations with the regulatory agencies, surface and mineral owners and other interested parties can create a very complicated scenario that requires an understanding of the law regarding environmental protection, bankruptcy and surety ship, along with technical expertise in land reclamation. This paper presents the engineering professional with a framework regarding areas of law that pertain to surety reclamation projects and negotiations with state and federal agencies and related parties. Though presented in the context of the coal industry, the principles discussed are generally applicable to the mining industry as a whole.

Jan 1, 2003

By L. D. Ricketts

AN older man looks back, perhaps wistfully, on a long and rather active experience, and possibly a popular and brief glimpse of some contrast between past and present may hold your attention for a few brief moments and prove useful. In the late nineties an engineer was .called on to de- sign and build two copper ore concentrating mills of 400 tons average daily capacity. There were larger mills than this at Washoe and elsewhere, but a 400 ton' mill was a large one as mills went over thirty years ago, and one might say a large mill of those days could crush a ton of copper ore in 216 seconds. In the mills I refer to steel construction and the conveying belts were introduced into the copper industry and rein- forced concrete came shortly after. Since then we in the West have ever been faced with a constantly de- creasing tenor in the grade of our copper ores and a constantly increasing demand for our product, and we have therefore been obliged to call for far larger castings and finished machines than were formerly used. The mechanical engineer has also enabled us to accomplish notable economies in power generation and distribution. Ore handling and crushing have been simplified and through the introduction of reagents to induce physical or chemical reactions, or both, our older methods have been vastly improved or even supplanted by new and better ones and our recoveries greatly improved.

Jan 1, 1929

By Ali Akbar Mottahedi

Chromate conversion coating is a process for making a complex layer at the surface of zinc galvanized steel which makes the metal more resistant to corrosion, especially at marine atmosphere, and increases the adhesiveness of color. In this work the influences of various compositions on commercial zinc galvanized steel sheet to the color of chromate conversion coating has been investigated at normal temperature and the factors that affect the control and optimization of the process have been determined. A bath composition of 20 g/liter Cr203 and 10 g/liter NaOH and a dipping time of 50 seconds at room temperature (25-30°C) make a desirable color of chromate coating. A slow agitation at a constant pH of I (with additions of NaOH or H2SO4) assures a constant bath condition and develops the color. This kind of coating has more corrosion resistance and this bath condition and composition are also more economical.

Jan 1, 2003

By R. Hogg, T. F. Dumm

"It is generally agreed that dust characteristics play a role in the development of Coal Workers' Pneumoconiosis (CWP). Unfortunately, there is a serious lack of information on what the characteristics of mine dust actually are and how they vary among different mining regions, coal seams, etc. This paucity of data can generally be attributed to the serious problems encountered in collecting sufficiently large quantities of dust for conventional analytical procedures.Personal samplers are widely used in coal mines for regulatory and enforcement purposes. Generally, these provide information only on the total (respirable) dust loading in the mine atmosphere and on the mineral matter (primarily quartz) content of the respirable dust. A procedure has been developed by which samples collected with a slightly modified personal sampler can be analyzed for particle size distribution, total mineral matter content and elemental composition, in addition to the standard mass and quartz measurements. These analyses could readily be performed on a routine basis. Shape analysis by Scanning Electron Microscope (SEM) could easily be included if appropriate shape criteria are established. Extension of the procedure to include the determination of complete size/specific gravity (composition) distributions is quite straightforward provided sufficiently large samples (at least 10 mg) can be collected. Typical sample sizes for a personal sampler carried by a miner for one shift range from about 0.5 to 2 mg.The basic procedure was developed and evaluated using synthetic mine dust prepared in the laboratory. Field tests in three working mines in Pennsylvania and West Virginia have confirmed the applicability of the approach to the real world. Particle size distribution measurements on mine dust collected in the modified personal sampler were found to agree closely with the results of simultaneous in situ measurements obtained using cascade impactors."

Mar 1, 1989

By Ted Klemetti, Gabriel Esterhuizen, John L. Ellenberger

"Advanced numerical models can be used to evaluate entry support systems in coal mines. However, these methods require specialized software and specialized skills to create the models and evaluate the results. Practicing support design engineers require a method to rapidly assess a proposed support system for a given geotechnical scenario. A prediction equation that can be used to assess roof support systems has been developed from the results of hundreds of FLAC3D analyses that were conducted during recent research. These models were validated against field cases and empirical design approaches and were found to adequately predict entry stability in coal mines. The understanding developed from the model outcomes was used to develop an equation to predict entry roof stability against large roof falls. Least-squares error analysis was conducted to find appropriate parameters for the nonlinear equation. The developed equation can be solved using spreadsheet software, allowing for rapid assessment of alternative support system performance in variable geological conditions. The performance of the prediction equation is evaluated against empirical design methods and against selected case histories of support practices at currently operating mines. Examples are presented that demonstrate the performance of the equation in variable geological settings. The stability factor (SF) prediction equation can be used as an assessment tool to assist in the design of coal mine roof support systems.IntroductionGround falls represent a significant proportion of injuries and fatalities in underground coal mines in the US. During 2013, ground falls were responsible for 4 of the 14 fatalities and 16.6 % of the 1,577 reportable lost-time injuries (MSHA, 2015). In addition, each year about 400 to 500 large roof falls are reported that can extend up to or above the bolted horizon. Large roof falls and associated ground fall hazards can be mitigated through improved support design.The research presented here particularly addresses the problem of large roof falls that extend more than 90 cm (3 ft) above the roof line of an entry and may extend above the bolted horizon. Smaller roof falls that fall out between supports or extend less than 90 cm (3 ft) above the roof line are excluded. These smaller roof falls can be controlled by appropriate surface support such as roof screen or other skin control methods. Also excluded are roof falls that are associated with an individual geological structure such as a slip of fault. Structure-related instabilities can be controlled by strategically locating individual roof bolts or other supports appropriate for the local situation."

Jan 1, 2015

By J. A. Barrera-Godinez

Traditional batch flotation tests produce a limited number of data points from which to evaluate the kinetics of the process. In this research, continuous weighing of froth, from a modified circular flotation cell, using a computer/data acquisition system., has been coupled with chemical analyses from intermittent froth sampling. This combination has permitted the experimental data to be smoothed such that the flotation kinetic parameters could be determined with enhanced confidence. To demonstrate the procedure, a galena ore was floated to permit flotation kinetics to be investigated as a function of cell parameters. It was shown that the kinetic data of this lead flotation most closely correlated with the Huber-Panu three parameter model. In addition the results illustrated the effect of froth thickness, froth scraper rate and air flow rate on the cell performance, in terms of mass flow, grade and recovery.

Jan 1, 1990

By Bora Derin

This work deals with the recovery of valuable metals from the ancient copper smelting slags located in Küre-Turkey. In this process, copper and cobalt were recovered in metallic form and/or as their compounds, whereas iron was recovered as magnetic oxide or pigment. Abrasive grit material was produced using reduced final slag. The process stages involved carbothermal reduction in a DC arc furnace, granulation, leaching, chemical precipitation, selective sulfidizing roasting and product preparations. In this paper, the process stages were described as theoretically and experimentally whereas slag and products were characterized in detail.

Jan 1, 2003

By Bora Derin

This work deals with the recovery of valuable metals from the ancient copper smelting slags located in Küre-Turkey. In this process, copper and cobalt were recovered in metallic form and/or as their compounds, whereas iron was recovered as magnetic oxide or pigment. Abrasive grit material was produced using reduced final slag. The process stages involved carbothermal reduction in a DC arc furnace, granulation, leaching, chemical precipitation, selective sulfidizing roasting and product preparations. In this paper, the process stages were described as theoretically and experimentally whereas slag and products were characterized in detail.

Jan 1, 2003

By Niels Verbaan

NioCorp is developing the niobium/scandium/titanium Elk Creek carbonatite deposit. The probable reserve announced by the company in 2017 indicated significant niobium (0.79% Nb2O5), titanium (2.81% TiO2), and scandium (71 g/t), and is composed predominantly of calcite, dolomite, and ankerite. Niobium is mostly (80%) contained in pyrochlore with the balance in various Fe-Nb-Ti oxides, which also host most of the titanium. Scandium is primarily deported in dolomite, with lesser quantities in pyrochlore and biotite. The process flowsheet recovers separate niobium, titanium, and scandium products. Scandium is extracted from whole ore hydrochloric acid leach solutions using solvent extraction and is further refined through a re-leach and precipitation process. Scandium leach residues are treated in a sulphuric acid sulphation process to recover separate niobium and titanium precipitates as well as to solubilize the remaining scandium. Both hydrochloric acid and sulphuric acid reagents are recycled within the flowsheet. This paper will discuss key bench and pilot test results of the niobium extraction and recovery circuits and will present a conceptual flowsheet developed by the project team for NioCorp at SGS Minerals.