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By Richard S. Klein

Frozen coal creates severe handling problems. Utilities require uninterrupted supplies of coal to meet their increasing coal consumption rates. Difficulties incurred due to frozen coal result in more costly downtime for the utilities. Air cannons, vibratory hammers and thaw sheds are examples of mechanical devices used to break, crack or thaw frozen coal. Recently chemical treatments have been developed as preventive measures. The freezing of coal depends upon a number of factors, of which one of the most significant is surface moisture. The more there is, the larger the frozen coal problem. Slide 1 depicts a graph of frozen coal compressive strength as a function of surface moisture. Below a certain minimum value the coal will not freeze. Above this point, compressive strength is essentially a linear function of moisture over the range practically encountered. By surface moisture is meant the free moisture on coal having a normal vapor pressure as opposed to capillary moisture or inherent moisture. In addition to the straightforward freezing of coal surface moisture binding particulates together, frost formation occurs due to temperature gradients which develop in rail-cars and stockpiles .

Jan 1, 1980

By Walter Kahn

Increasing consideration is being given to simplifying traditional methods of tracing pipelines and maintaining required temperatures of stored fluids. Because of their reduction in capital costs, virtual elimination of maintenance. ease of control and "cleanliness"; interest in electrical techniques has accelerated. 1,2 Resistance cable and other heaters have been given some attention. but less well known in the recent introduction of thermal conductive coatings. This paper is addressed to the use of thermal conductive coatings for heating fluid-transport piping and storage tanks. Emphasis will be given to the simplicity, efficiency, and versatility of design and application which their unique properties further contribute to the general economics of electrical heating.

Jan 1, 1965

By Kenneth Maser, Douglas W. Ounanian, Joseph S. Boyce

Foster-Miller Associates, Inc. (FMA), under contract to the Department of Transportation (DOT) and the Urban Mass Transit Administration (UMTA), is currently developing an Extruded Tunnel Lining System (ETLS). The ETLS would reduce ground support costs in machine bored tunneling by eliminating the need for temporary support, and by slip-forming the final concrete lining directly behind the Tunnel Boring Machine (TBM). The system can advance at variable rates, from 0.6 to 3.7 m (2 to 12 ft) per hr, by combining three systems: a very high early strength concrete, continuously produced and delivered by a concrete process system; a slipform/bulkhead system for supporting the concrete prior to strength gain and exposure; and a control system for form/bulkhead alignment and concrete process control. Large-scale tests are planned to demonstrate the system in a 3 m (10-ft) diameter steel "tunnel".

Jan 1, 1981

By William O. Rasmussen

Exploration requires processing highly varying kinds and amounts of geologic information. Successful discovery dictates that this be done quickly with maximum confidence. Most phases of exploration are more or less applicable to computer reduction on a routine basis. The use of digital computers to reduce raw data into interpretable form, lets the exploration geophysicist concentrate on interpretation and presentation, and to consistently apply more sophisticated and comprehensive analytical techniques, not practical before. In applying these concepts for the past several years, various efficient programs have evolved which provide more complete evaluation of all data including the pro- vision for more unique solutions. This has resulted in greater refinement and ability to select the most advantageous drill sites in a minimum time at a minimum cost or, in rejecting as soon as possible a project on which additional effort is no longer justified. Practical examples of computer applications in magnetics (air and ground), induced polarization and resistivity are discussed.

Jan 1, 1969

By B. Stewart

Recent ore pass failures have underlined the need for improved designs, standards, structural monitoring methods, and better hang up prevention and removal techniques. Researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) are investigating methods to improve safety during transport of ore in ore passes. Design criteria and hang-up prevention and remediation strategies involve studies of the effects of static and dynamic ore and waste rock loads on chutes, walls, gates, and support structures. Particle flow analysis methods were used to simulate the response of various ore pass designs to a wide range of ore loading conditions. A full-scale mock-up of actual ore pass and chute assemblies was duplicated and tested for load response. Data from a particle flow code and the mock-ups were com-pared. Loads on an active ore pass chute were measured.

Jan 1, 1998

By R. H. King

Underground coal mining machinery utilizes portable electric sables, "trailing cables." to obtain power from load centers or distribution boxes. Cables are frequently damaged since mobile equipment, poor lighting, and restricted space are inherent to coal mining operations. Normally, the damage is repaired by splicing--the joining of one or more severed conductors and replacing insulation and jacket. Figure 1 illustrates a typical single conductor splice. Although the repair seems simple, difficulty of the splicing process is exemplified by the many safety hazards and frequent production delays that result from defective splices. Forty-two cable splice related injuries were reported to the U.S. Bureau of Mines in 1972 and 1973. Additionally, 17 splices related fires were reported in the three year period prior to December 1972. Assuming the damaged area is quickly located, an average splice time for a two conductor cable is twenty minutes. Some operators estimate this delay is incurred once per day per operating section. If one ton per minute is averaged throughout the shift, each unit could loose 4800 tons per year from splice delays. An estimated cost for materials and labor to make a splice is $20. The expenditure could result in a $4800 annual cost per section. The estimated expense does not include wages of other personnel waiting for the repair to be completed. Nevertheless, labor and materials cost is minor compared to the income lost from decreased production.

Jan 1, 1975

By N. A. Abdel-Khalek

An experimental study was carried out to compare the results of laboratory column flotation versus conventional flotation for the cleaning of fine coals of different rank and their oxidized samples as well as discrete size fractions. Surface oxidation caused a significant reduction in the flotation yields achieved with both methods. However, the column flotation produced concentrates? of lower ash content. The recovery -size curve achieved with column was similar in shape to that obtained with conventional cell, with superior results in the region of fine fractions. The influence of some column operating parameters was also discussed.

Jan 1, 1990

By D. W. McGlashan

Zeta potential changes were determined as a function of pH, metal ion, and surfactant concentrations. Prom the analysis of data, flotation experiments were carried out to correlate float-ability with the differences in zeta potential. Cassiterite in water bears a negative zeta potential, The zeta potential of cassiterite is sensitive to pH changes; the electric double layer arises from the preferential adsorption of H+ and OH- ions and subsequent ionization of the hydroxylated surface. It is suspected that hydronium-ion concentration may cause reversal in the sign of the zeta potential. The ZPC was found to occur at pH 3.4. Metallic ions and the hydrated ions thereof affect the zeta potential of cassiterite in differing degrees of intensity. Without prior activation, sulfonated surfactants do not change the zeta potential of cassiterite. Sodium alkyl aryl sulfonate is especially active on lead-activated cassiterite and ferric-activated cassiteriten Microcalorimetric fiests confimed the activity of ions on cassiterite and showed the hydrated character of cassiterite smfaces. Close correlation between zeta potential and microflotation results was achieved.

Jan 1, 1969

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 Harvey P. Knudsen

This paper illustrates the application of geostatistics to a roll front type uranium deposit located in Wyoming. The steps involved in calculation of experimental variograms, variogram modeling and verification of the resulting models are described in detail. The resulting spherical variogram models for grade thickness and thickness show strong geometrical anisotropies. The major axis of anisotropy for both variables is approximately parallel to the axis of the roll front and the minor axis perpendicular to the roll. This model confirms the technique of drilling "fences" across the roll front, where the drilling is much closer together than the fences along the roll.

Jan 1, 1978

By A. M. Gaudin

A new method of measuring the viscosity of unstable suspensions has been developed, using a Heinz viscometer. The technique was applied to kaolin-water suspensions. Spreads in viscosity with lime additive were measured.

Jan 1, 1962

By R. E. Wagner

Consistent increase has been the mark of North American potassium (K) consumption. In 23 of the last 25 years there was upward progress The pace of usage has quickened in the past three or four years This, together with a predicted accelerated future demand, has created unprecedented interest -and activity in the potash industry. Potassium enjoyed a ninefold increase in consumption from 1940 to the present time in North America (Figure 1). Since 1950, it increased from just over a million tons of potash (K20) annually to nearly three million tons in 1964. World-wide usage exclusive of mainland China is now about 10 million metric tons. Some predictions call for another doubling in consumption in the next 10 to 15 years, About 20 percent of the four million tons of K20 produced in North America is now exported overseas and this percentage is likely to increase in the years ahead. Ten years ago, exports represented only 3-1/2 percent of total K2O production from this continent.

Jan 1, 1966

By D. L. McCain

The movement of solids by pipeline is an art dating back well over 100 years as evidenced by many references in the literature. Even though all of the early pipeline transport systems were based on trial and error and relied mainly upon the designer's experience, hydraulic transport offered distinct advantages in convenience or cost for the chemical, mining, and civil engineering industries. It became well established for in-plant process lines, dredging, waste disposal, and other uses almost exclusively for short distances. During more recent times, much research work has been done in an attempt to understand the underlying principles involved in transporting solids in a fluid. Design criteria for pumping slurries have evolved to the point where pipelines designed for distances of several miles to several hundred miles can be accomplished successfully. Consolidation Coal Company designed and built a 10-inch diameter 108-mile long line1 for transporting coal in the 1950's and operated it from 1957 to 1963 when it was placed in mothballs because of falling freight rates for rail shipment. More recently, the 273-mile Black Mesa Pipeline2 was built and is operating. There are other examples of long distance pipelines,3 but all are for specially prepared fine slurries which allow the pipeline to be operated more economically.

Jan 1, 1975

By H. L. Lovall

Huge banks of preparation plant refuse and other non¬saleable materials have accumulated over the years in all major United States coal producing areas. These banks, esthetically and commercially undesirable, can cause air and water pollution and land reclamation and mineral conservation problems for the industry and nearby communities Although some refuse banks have been reworked to recover saleable coal, all remain and accumulation continues. Even those previously processed continue as potential hazards. Among the several problems created by refuse banks, in situ combustion is most treacherous. Of the millions of tons of major accumulations, there are at least 450 refuse banks on, fire at this time Attempts to extinguish such fires are costly, impractical and generally unfruitful. Studies are in progress to evaluate the potential of processing such materials to eliminate the combustion capability and to yield usable fuel and nonfuel products. Aspects of the study now in. development for coal refuse include: (a) evaluation of characteristics (size, sink-float, ash, sulfur and calorific value) of the coal refuse materials which are known to be highly variable, (b) development of an ignition test having significance for in situ conditions, (c) study of processing capabilities (comminution for liberation, pilot plant washing tests), and (d) investigation of potentially significant properties of fuel and nonfuel products which could be altered to enhance their market potential.. Among the latter products are lightweight aggregate, fill for mine slushing operations, construction, etc: Plans are to extend the studies to include the design, erection, and test processing of refuse with a transportable plant,; which could provide basic economic and product utilization data from several locations

Jan 1, 1964

By Daniel W. H. Su

A nearly 305-m- (1,000-ft-) wide sandstone channel was projected to run through the mid panel area of a 457-m- (1,500-ft-) wide longwall panel in a southwestern Pennsylvania coal mine. This sandstone channel was known to cause serious longwallface roof control problems in the mine?s B-panel area in 1998 and 1999; and most recently, it induced many large face cavities and caused a substantial production delay in the preceding panel. For the two B panels mined in 1998 and 1999, hydraulic fracturing of the massive sandstone was conducted to facilitate better caving, thus relieving cantilever compressive stress at the longwall face. Vastly improved longwall face condition was observed and four weeks of mining delay due to bad roof conditions were eliminated. The implementation of the hydraulic fracturing technique, results of underground observation and measurement, and results of numerical modeling were summarized in a paper presented in the 20th International Conference on Ground Control (Su et al., 2001). This article is a summary of the activities that took place during a four-month period (October 2011 through February 2012) at a Consol Energy longwall mine southwestern Pennsylvania to improve face conditions and safety of underground personnel during mining of the 457-m- (1,500-ft-) wide longwall panel. The elevated concern for safety was driven by adverse face conditions encountered while mining the preceding longwall panel. Many of the problems were attributed to a thick and massive sandstone channel. A joint task force consisting of coal operations engineering, Pennsylvania operations engineering and CNX Gas personnel was formed in August 2011, which recommended drilling four hydraulic fracturing holes along the center axis of the sandstone channel to reduce pressure and improve face conditions at the longwall face. To further provide detailed monitoring of the longwall face and to evaluate the effectiveness of the hydraulic fracturing program, the Longwall Visual Analysis (LVA) software (Hoyer, 2011) was installed in early December 2011 to track the face pressure and c

Jun 1, 2013

By R. G. Darmody

Longwall coal mining in southern Illinois occurs beneath some of the best agricultural land in the U.S. This region is characterized by highly productive, nearly level, and somewhat poorly drained soils. Subsidence from longwall mining causes changes in surface topography which alters surface and subsurface hydrology. These changes can adversely affect agricultural land by creating wet or ponded areas that can be deleterious to crop production. While most subsided areas show little impact from subsidence, some areas experience total crop failure. Coal companies are required by law to mitigate subsidence damage to cropland. The objective of this study was to test the effectiveness of mitigation in restoring grain yields to their pre-mined levels. The research was conducted on sites selected to represent conventional mitigation techniques on the predominate soils in the area. Corn (Zea mays L.) and soybean [Glycine max.(L.) Merr] yields in 1988, 1989, 1990, and 1991 from mitigated areas were compared to yields from nearby undisturbed areas. There was no significant (a=0.05) difference in soybean yields averaged over the four years. Average corn yields, however, were significantly lower than reference areas. The impact of subsidence and mitigation is variable and site specific. Results were also related to weather. In wet years, yields in mitigated areas tended to be depressed. This research demonstrated that mitigation of subsidence damage can be successful.

Jan 1, 1986

By W. D. Bachman

A study has been made of wet, autogenous grinding of disseminated copper ores, including testing of a large number of samples from Kennecott Copper Corporation's Chino mine. The efficiency with which the various samples could be ground was found to vary over an extremely wide range, even among samples taken from different locations within the same ore body. These variations in grindability can be qualitatively correlated with the composition of the rock and the fracturing and alteration that had occurred. Because of the large-scale non-homogeneity of disseminated copper ore bodies, extensive and careful testing of autogenous grinding is needed. An accurate correlation of the grinding data from various samples with the geology of the ore body and with mining plans will indicate if variations in grinding mill throughput can be avoided in practice by mixing or blending of mill feed and if, therefore, autogenous grinding can be applied successfully.

Jan 1, 1970

By Ren Bryce

The ninth annual Mineral & Metallurgical Processing Division (MPD) student poster contest was held in February at the SME Annual Conference & Expo in Minneapolis, MN. A total of 33 students presented their work at the contest. The competition began in January when the students submitted a one-page abstract for judging. In February, they prepared and presented a poster that explained their research. A panel of judges went to each student and listened as the students explained their research in five minutes. The students worked hard at their research and then set aside time to complete all the necessary steps to enter the contest. The MPD recognizes the effort required to enter and, as a result, provides monetary rewards to all participants. As in past years, there are separate levels of competition for undergraduates and graduates, and the prizes are designated accordingly. At the graduate level, first place receives $1,000, second place $500, third through seventh $200 each, and all others $125 each. At the undergraduate level, first place receives $1,000, second place $500, third place $250, and all others $125 each.

By William I. Weisman

Natural sodium sulfate is obtained from both brines and solid deposits. The brines almost always contain other salts with sodium chloride predominating. They may be obtained from surface occurrences, such as Great Salt Lake or from shallow subterranean deposits. Althought many sodium sulfate minerals are known to exist, only three are of commercial significance. These are thenardite, the anhydrous salt; mirabilite, the decahydrate; and glauberite, the double salt of sodium and calcium sulfate. The reader is referred to Weisman (1983) for details on mineralogy and geology of sodium sulfate minerals. Sodium sulfate deposits, either in the form of brine or solid minerals, are found in many parts of the world. Natural sources, by far, provide the primary supply of commercial grades in Canada, Mexico, Spain, and probably in the U.S.S.R., Chile, Argentina, and Turkey. In the United States, production of natural material and synthetic (including by-product) are about equal in volume and have been for many years.

Jan 1, 1984

By M. Karmis

Subsidence planning and control must be an integral part of mine design in order to minimize the economic impact of underground mining on the surface. Pre-calculation of surface deformations which may cause damage to surface structures must be performed and dam-age criteria must be established, if the response of structures to such movements is to be determined and the extent of damages to be assessed. In this paper the Surface Deformation Prediction System (S.D.P.S.), which can be used to predict accurately the vertical and horizontal parameters of surface movements due to underground mining, is discussed. The Subsidence Response Modeling Program (S.R.M.P.). which can be applied to evaluate the response of buildings to subsidence-induced movements, is also reviewed. Finally, an example is presented demonstrating the applicability of these techniques for subsidence design and control.

Jan 1, 1990