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By K. V. Raj, C. A. Berry, A. T. Weakley, A. L. Miller, P. R. Griffiths, D. A. Parks

Diesel particulate matter (DPM) has been classified as a carcinogen to humans by the International Agency for Research on Cancer. As a result of its potential carcinogenic nature, DPM exposure is regulated by the Mine Safety and Health Administration. Currently, diesel emissions in the workplace are monitored by collecting the aerosol onto filters, which are then sent to a laboratory for thermal-optical analysis using the NIOSH method 5040. This process can take days or even weeks, and workers can potentially be exposed to excessive levels of DPM before the problem is identified. Moreover, the delay involved in getting the loaded filter to the lab inevitably means the loss of some of the more volatile organic carbon. To remedy this delay, researchers from the National Institute for Occupational Safety and Health are seeking to develop a field-portable, real-time method for measuring elemental and organic carbons in DPM aerosols. In the current study, the use of mid-infrared spectrometry was investigated. It is believed that mid-infrared spectroscopy is more suitable for use in a real-time field-portable device than thermo-optical analysis methods. This article presents a method for measuring organic carbon (OC) and elemental carbon (EC) in DPM for a broad range of OC/EC ratios. The method has been successfully applied to laboratory-generated and mine samples.

By K. N. Han

Coal is becoming increasingly important as a major energy source in the face of the world's depleting energy mainly based on oil reserves. Coal is by far the most abundant fossil fuel both in the United States and abroad. Currently, because of increased mine mechanization, the fineness of preparation plant feed is increasing. Further, in the future as the grade of coal diminishes and the sulfur content increases, upgrading preparation of coal is very important. Because the density of coal is less than that of rock materials that occur as impurities, coal is separated from such waste largely by gravity-controlled processes for particle size between 5 inches and 28 mesh. If the size of coal particles is below 28 mesh, froth flotation is a good method for upgrading fine coal. Previously, numerous investigators have tried to upgrade coal values by froth flotation(1-16) and have achieved moderate success. However, the recovery and grade of coals in the concentrates are not always satisfactory, especially when the particle size is small. In general, when the size of coal is below 100 mesh, the above methods suffer from poor grade and low recovery. The reason for this is that as size decreases, the effects of gravity diminish, and other forces take effect.

Jan 1, 1985

By J. M. Dean

With the continued downward pressure on coal selling prices, mine management must make its operations as efficient as possible. The problem is the same one throughout the mineral industries, streamlining operations to maintain competitive mining costs (Born, 1991). There has been a great deal of research into better using production manpower. But the story is different for operations support personnel. Traditionally, planning man-power requirements are done annually, with modifications to the operating plan occurring generally quarterly. On the other hand, the demands on manpower are often dynamic, being responsive to changing productivity levels ,mine conditions (including water influx, bad roof, poor floor)and unanticipated project requirements (responses to machine breakdowns or a new section setup requirement because of a drop in coal quality in another area). Such changes may impact the manpower structure significantly. At times they may cause serious labor relations problems concurrently. Realignments and the generation of instability in the workforce because of active job switching (bidding) are a result. Most responses by coal operators are reactive rather than proactive, a situation that could be mollified by more accurate and detailed planning of predictable manpower requirements. A manpower planning tool is needed that takes into consideration such things as changing productivity levels and conditions as manhour requirements for different work areas are planned, rather than blindly allocated through traditional staffing modes.

Jan 1, 1995

By Yi-Hsuan Chen, Jürgen Brune, Candace S. J. Tsai, Alejandro Munoz, Connor Krause

This study highlights the significant presence of submicrometer- sized airborne particles in underground coal mines, especially around the belt conveyor drift areas. Using realtime instruments and gravimetric samplers, the assessment revealed that particle concentrations were notably higher in the belt entry compared to other locations, with a strong presence of submicrometer- and nanoparticle-sized dust. The study’s findings emphasize the importance of addressing small particle exposure, as these particles, composed of harmful substances like calcium, copper and iron, can pose serious health risks to miners. This research emphasizes the importance of improving air exposure estimation through more effective monitoring and characterization techniques to better understand and reduce workers’ exposure to hazardous airborne particles in the mining environments.

Apr 1, 2025

By Yues Bertube

Molybdenite and chalcopyrite are two often-associated minerals. In Quebec, the Gaspe Copper Company, a subsidiary of the Noranda group, currently operates a molybdenite flotation circuit to recover a one percent trace of this mineral in the chalcopyrite concentrate. The low levels of molybdeni 2 preclude the use of flotation to remove molybdenum directly from the ore while scavenging of chalcopyrite concentrate for molybdenite yields a concentrate of the latter of somewhat inadequate quality. Such a situation could possibly best be solved by hydrometallurgical means, if molybdenite could be leached selectively from the chalcopyrite concentrate. Work in the field of extractive metallurgy was initiated about 22 years ago in the laboratory of the department of mining and metallurgy at Laval University, Quebec. Following a literature search, two objectives were selected. The present talk will outline some of the results obtained to-date and it is hoped the ensuing discussion of the paper can raise questions of immediate assistance to us for the future. First, as an immediate objective of-practical use, the oxidation rates for molybdenite and chalcopyrite in alkaline media would be studied under conditions of possible industrial application. Secondly, the kinetics of mass transfer of gases in pressure reactor are to be studied. Solubility data for various gases in aqueous solutions have been gathered by a few investigators, to mention the work of Pray1, Wadsworth2, Pawlek3 and Gerlach. Scattering in experimental results and discrepancies between authors are ominously present. Kinetics of mass transfer have somewhat been more neglected. A systematic investigation by the school of Berlin has greatly helped in the design of impeller most suitable for gas dispersion, without much reference however to the solid dispersing ability of the various designs. Variables affecting rates of gas transfer to the solution have not been studied. Studies on the aqueous oxidation of sulfide minerals are much more numerous. While molybdenite has been relatively less studied, work has been carried in two areas namely in alkaline oxidation of MoS2 , work performed by Dresher2 and Wadsworth, and in the hypochlorite leach of molybdenite by Bhappu4 and co-workers, These two methods showed appreciable rates of leaching for molybdenite. In general, comparisons between rates of oxidation of this sulfide with that for chalcopyrite have not been made.

Jan 1, 1972

By B. J. Scheiner

A ferrous chloride-oxygen leaching system was investigated by the Federal Bureau of Mines as a means of re-covering copper and silver from a sulfide concentrate that had been pretreated to remove a majority of the antimony. The pretreated concentrate contained Cu, Ag, Pb, Zn, Sb, and As. Parameters affecting metal extraction, such as temperature, pressure, amount of ferrous chloride, and initial hydrogen ion concentration, were studied. Copper extraction of 98 pct was achieved by leaching 4 hours at 40 pounds per?square inch gage (psig) and 1000 ?C. Copper was recovered from leach solutions by cementation with iron, and the resulting ferrous chloride was recycled. Leaching the residue with cyanide followed by electrowinning recovered 99.7 pct of the silver. Iron, Sb, As, Pb, and S reported to the tails.

Jan 1, 1978

By M. Z. Rashad

The purpose of this paper was to compare the covariance and multiquadric functions in same mining and geological applications. The basic principals of the two techniques are covered briefly. Similarities and dissimilarities of the covariance and multiquadric functions are discussed geometrically, mathematically and practically. A 14 by 16 kilometer square area in Baharia Oasis, Western Desert of Egypt, was selected for a detailed comparative test. The gravity anomalies of forty-eight test stations were computed by using the data of sixty-three control stations. The results indicated that the covariance function is quite better than the multiquadric one. On the other hand, the multiquadric function more simple in computation than the other one, which needs to precalculations such as semivariogram and covariogram. Moreover, multiquadric equations are based on geometrical and physical considerations rather than covariance functions.

Jan 1, 1990

By J. G. Groppo

Lowering of filter cake moisture of ultra-fine coal to a 20 percent level using conventional vacuum filtration could be achieved using a combination of metal ion and surfactants. Pretreating coal slurry with about 0.2 Kg/ton of a surfactant and 50 ppm of copper or 10 ppm of aluminum ions provided filter cake containing 22.8 percent moisture. The lowering of moisture is explained due to formation of hydrophobic micro-agglomerates which facilitates dewatering.

Jan 1, 1994

By M. Akram

Stability assessment of entry roofs is an essential precursor to all underground design. Both multi-seam interaction and longwall mining can subject entries to radical changes in the surrounding stress field. Such loading changes frequently produce instability and failure in the roof, floor and pillars. Roofs are shown to be vulnerable to stress-induced failures, particularly when the load is unsymmetrical. To predict the effects of changes in stress field, roof failure conditions under increasing loads were studied using finite element analysis and body loaded photoelastic models. A large range of geologic conditions were evaluated and incorporated into the model using Monte Carlo methods. Entry analysis using the model showed the roof to be particularly vulnerable to shear with the location of the failure site changing to meet loading and geologic conditions. Results were correlated with field data to determine stress levels at which failure could be expected to occur. Based on this research a roof stability model SESAME was constructed for roof stability evaluation under specified loading conditions.

Jan 1, 1993

The floatability of a bituminous coal in NaG solutions was evaluated using a modified Hallimond tube to delineate the role of the electrostatic interaction between bubbles and particles in determining the coal hydrophobicity. Zeta potential measurements showed that bubbles are negatively charged in the entire pH range tested, while coal particles are positively charged below pH 6.0 and negatively charged above it. Also, both sodium and chloride ions were confirmed to act as indifferent ions without any specific effects for both coal particles and bubbles. Flotation as a function of pH exhibited a maximum and minimum at low salt concentrations which is shown to be determined mainly by the coal hydrophobicity as measured by a new hydrophobic levitation technique. At high salt concentrations (above 0.1 mole/dm3), the flotation without such maximum or minimum is controlled by the electrostatic interaction between the bubble and the particle.

Jan 1, 1992

By M. C. Williams

The solution of the dynamic population balance model (PBM) of a closed grinding network consisting of a mill, sump, and cyclone is problematic. The fact that the dynamic PBM model equation solution to the Inverse Problem for grinding systems is degenerate or underspecified is demonstrated. Two numerical solution approaches to the Inverse Problem are used. These are: 1) providing additional constraints on breakage selection functions or 2) performing the Arbiter-Bhrany (or other) normalization of the selection functions. Actual experimental anthracite batch grinding data is used to demonstrate the non-unique functionality of the batch dynamic mill selection and breakage functions for a real physical system. The Levenberg-Marquardt algorithm for systems of constrained non-linear equations is used to solve the batch dynamic PBM grinding equations to obtain the grinding selection and breakage rate functions. Different solutions to the same PBM transport equations are provided. The mill, sump and hydrocyclone were modeled as a CSTR operating at various retention times. Batch dynamic PBM data was used to provide the mill kinetic and breakage selection function data. Two different solutions were obtained depending on the numerical solution approach. The severity of the non-uniqueness problem for dynamic grinding is demonstrated. Each solution approach to a dynamic PBM with transport, while giving the same prediction for a single batch grinding time, gives different solutions or predictions for mill composition for other grinding times. This fact makes dynamic nodal analysis and control problematic. The fact that the constraint solution approach gives a solution may suggest that normalization for closed networks is not necessary. Differences in solutions to the PBM cannot be excused away by inaccuracies in the data used to model the grinding phenomenon.

Jan 1, 1995

By Burton H. Boyum

The paper generally reviews the iron ore occurrences and regional geology of Western Australia, but features in particular the mesa deposits of PJasic Materials - Cliffs International. Initial production is planned from a aeries of mesa deposits of Eocene-Oligocene age. The ore is oölitic to pisolitic goethite and hematite. Source of the iron in the mesa deposits is thought to be from the Precambrian iron-formations. The geology and occurrences of the mesa iron ore deposits are summarized and illustrated.

Jan 1, 1964

By Daniel A. Payne

For many years underground mining in the Sydney Coalfield has suffered from the effects of high horizontal stresses. It is only in the last 15 years that they have come to be recognized, understood, predicted and even avoided. This paper relates experiences in three coal mines in three different seams in the Sydney Coalfield. The effect of the direction of the principal horizontal stress on the direction of drivage of gate roads, access roadways and longwalls is described. Results of a monitoring program to measure the change of magnitude and direction of the principal horizontal stress in the gate roads as a result of longwall mining are also presented as well as the effect of the direction of principal horizontal stress on the shape of sandstone/gas outburst cavities.

Jan 1, 1998

By Gerald W. Elger

Research at the Albany Metallurgy Research Center has shown that high-purity rutile can be produced from relatively low-grade ilmenite obtained from a massive rock deposit. Ilmenite is first smelted in an electric-arc furnace to separate the iron and produce a slag enriched in titanium dioxide. Titania slag mixed with a phosphate flux is then oxidized to synthesize rutile and form a phosphate-glass matrix which contains the impurities. Attrition scrubbing the treated slag in dilute solutions of phosphoric or sulfuric acid liberates the rutile, which is concentrated by physical methods. Tests show that synthesized rutile containing 95 to 97 pct titania responds to chlorination at the same rate as natural rutile.

Jan 1, 1973

By A. E. Isaacson

The U.S. Bureau of Mines is investigating a systems approach to metals recovery from leach liquors produced by in situ leach mining techniques. A successful in situ leaching process requires a thorough under-standing of the complex interrelationships that exist between leaching chemistry and metals recovery. Laboratory research is addressing these interrelationships in the solution mining of a copper oxide deposit. Laboratory tests have been conducted to gather baseline data related to the design and operation of continuous leaching-solvent extraction-electrowinning circuits. This paper addresses the findings of the baseline studies. Specific results include the characterization of simulated in situ leach liquors produced by leaching chrysocolla and chrysocolla-atacamite-bearing copper ores. Metal recovery procedures, utilizing four commercial solvent extraction reagents, are also characterized, and potentially troublesome leach liquor contaminants that may complicate waste management procedures are identified.

Jan 1, 1990

By G. G. O. O. Uwadiale

Starting from a crude ore assaying 45.6% Fe, a fine-grained oolitic iron ore was concentrated by the oil agglomeration technique to 90% Fe recovery and 65% Fe assay. The ore required grinding to minus 5 µm to effect adequate liberation, and the technique yielded optimum results at pH 9. The roles of pH, collector, and bridging liquid concentrations on selectivity and yield of iron minerals in the concentrates are discussed.

Jan 1, 1991

By Mark P. Walsh

In recent years in situ leach mining has emerged as a viable technology for the recovery of uranium from strata in South Texas which contain relatively low concentrations of uranium ore. Because the ore bodies lie within groundwater aquifers, a significant determinant in the economics is the requirement that such aquifers be protected from contaminantion. Since ammonia is one of the constituents of the leach solutions now being field tested, one environ- mental problem to be resolved is the removal of ammonia at the end of mining. A second related question is the fate of the ammonia which is not removed by the restoration procedure. This paper considers the displacement and migration of ammonium in a flowing electrolyte with concomitant ion exchange. The ion exchange is an important feature since, during the solution mining phase, ammonium saturates the mineral exchange sites and must be removed from these sites. A mathematical model is used to simulate this process and the model is tested against the results of laboratory experiments. It is found that the simulations are adequate if an appropriate selection of parameters is made. The model is then used to investigate the effect of cation composition and concentration of the restoration medium as well as dispersion on the overall effectiveness of the process. It is concluded that increasing the concentration of monovalent ions in a solution containing a mixture of both monovalent and divalent ions decreases the adsorption selectivity of the divalent ions with respect to all monovalent ions including ammonium. Thus increasing the ionic concentration of a restoration fluid by increasing the concentration of a nonselectively adsorbed (with respect to ammonium) ion may have a very limited benefit. Dispersion attending the flow of fluids in a porous medium is also shown to be an important factor. The effect of dispersion can greatly reduce the benefits of having a displacing cation which is adsorbed selectively with respect to ammonium. Since dispersion increases almost linearly with fluid velocity, an optimum displacement rate may exist.

Jan 1, 1979

By S. D. Bearden

The world's reserve base is adequate for at least 100 years at the current consumption rate. China, India, and the U.S. are expected to remain the leading producing countries. The U.S. will continue to be the largest consumer of the production. None of the known substitutes for barium sulfate are expected to impact existing applications. World production in 1995 was 4,410Mt. This is about 50% of the projected capacity. Consumption is directly proportional to hydro-carbon well installation activity. Imports are expected to continue to supply more than half of the U.S. requirements.

Jan 1, 1997

By Robert E. Frey

Regardless of the mechanical design features of a particular air classifier certain basic principles apply. Specifically , there are two forces at work: 1. An air drag force 2. An inertial or centrifugal force. The air drag force has an increasing influence as particles become smaller. A very small low mass particle is easily carried along with an air stream even when turning a corner. Thus, fine particles follow the air away from the classifying zone. Inertial forces increase as the mass of a particle gets larger. Thus oversize particles tend to obey Newton's laws and respond to centrifugal forces or simply continue in a straight path when the airflow changes direction.

Jan 1, 1985

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

The separating efficiency of a flotation column is largely limited by the degree of back mixing of tailings into the froth zone, and the recovery is limited by the degree of short-circuiting of feed to the tailings. Current columns are typically constructed very tall (30 to 40 ft) to limit the effects of back mixing and short-circuiting. These effects can also be reduced in a much shorter column, provided that the flow in the column approaches plug flow. In this work, horizontal baffles were shown to improve the performance of a 6 -ft laboratory-scale flotation column treating a poorly floatable coal. Tests with variations in the baffle positions showed that baffles are needed both above and below the feed inlet to achieve the greatest benefit. Tracer tests with a fluorescent dye in water showed that baffles reduce the amount of feed water entrained in the froth at any given coal recovery.

Jan 1, 1996