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By Fernando Romero Lage

"Crushing and screening theory and application has remained fairly consistent in the last 50 years. The application of such equipment is guided by varied formulaic conventions and rules that due to the entropic nature of the process, remains more an art than a science. The variability of conditions creates an environment in which trial and error becomes the principal means of process balance and control. This paper illustrates some of the theories behind the process, plus other assumptions, postulates, myths and misconceptions that exist within the crushing and screening industry.INTRODUCTIONContinuous material balance calculations are habitually performed in the design of new comminution circuits as well as in the valuation of existing circuits. A continuous material balance calculation is one in which the input rate of material is equal to the output rate for each unit functioning in the circuit. At continuous analysis, there is no accumulation or losses of material within the system, as it is when performing a discrete event analysis.In order to produce viable and manageable mine-to-mill material, whether it is ready to leach or ready to mill, we must reduce the material in a series of stages. The power demand increases as the material size decreases, as it is when folding a piece of paper successively. As with the paper, there is a crushing size limitation that is a consequence of the mineral properties such as work index, moisture, viscoelasticity, etc. Comprehensive knowledge of crushing plants in both the aggregate and the mining industries show that, after three stages of crushing, a particle size distribution originating from a blasted deposit can be reduced from an nominal maximum size of 500 mm to a nominal maximum size of 12 mm. if the last stage of crushing is set in closed circuit, the screen openings will be able to yield a smaller top size.Achieving steady and continuous material balance poses major difficulties as crusher lose their settings, screens blind or peg, and material characteristics change geographically or seasonally. Overloading conditions in crushers and screens are nothing but counterproductive, and the net losses of an unbalanced circuit can be overlooked when mining operators are paying a lot more attention to the evermore complex systems downstream.It is not simply the crushing of the mineral but achieving the right size for the downstream milling process that will yield the maximum amount of energy savings."

Jan 1, 2010

By Mark S. Sanders

This report is a review and synthesis of the published literature dealing with personal equipment items used by low seam coal miners. This report reviews the following items of equipment: headgear, outer garments, respirators, cap lamp, gloves, knee pads, footwear, boots, helmets, ear protection, eye protection. Recommendations for further research and development are included.

Jan 1, 1978

By G. R. Hopkins

According to reports received by the Bureau of Mines, Department of the Interior, as of January 1, 1934, there were 591 completed refineries in the United States, an increase of 86 ever the total reported at the beginning of 1933 and the largest total ever recorded. It should be noted that the 1934 total, although large, probably does not include more than half of the "pot-still" plants of 1 barrel to 50 barrels daily capacity which have sprung up within the last 2 or 3 years and about which very little information is available. However, the combined operations of these snail refineries are of negligible importance as altogether they refine less crude than one plant of average size. Of the completed plants, 454 were operating on January 1, 1934 and 137 were shut down. In addition, 13 refineries were under construction on January 1, 1934. Compared with the previous year these data indicate a marked increase in the number of operating plants, little change in the number of inoperative plants, but a decline in' the number being built. The material gain in the number of operating plants resulted primarily from the construction off approximately 25 refineries, averaging about 100 barrels capacity in the Kooky Mountain district, as well as from the addition of about 20 plants in the East Texas field.

Jan 1, 1934

By Edward Keller

The work covered by this report was undertaken at the request of Dr. J. A. Holmes, late Director of the Bureau of Mines, to whom the writer had been recommended by C. W. Goodale and E. P. Mathewson, of Butte and Anaconda, Mont. The director's offer was accepted for the honor it conferred and for the useful results that might be promulgated by the work in the technical field covered. The investigation was facilitated by permission to visit various works and sometimes by contributions of important definite information on a given subject. It is therefore with pleasure that acknowledgment of courtesies is made to the following corporations and gentlemen: Anaconda Copper Mining Co., Raritan Copper Works, Baltimore Copper Smelting & Rolling Co., United States Refining Co., American Smelting &, Refining Co., B. B. Thayer, A. C. Clark, A. L. Walker, William H. Peirce, E. A. Cappelen Smith, H. H. Alexander, F. C. Newton, S. Rolle, R. W. Deacon, N. W. Pierce, O. C. Martin, C. N. Sappington, James K. Thomson, W. G. Derby, and the assistants of the writer, K. W. McComas and W. L. Raup. In this report considerable space has been devoted to general and theoretical principles on the ground that under modern conditions the best results in any field of activity can be attained only with the a. id of an adequate knowledge of the best theories underlying the practice. The diffusion of such knowledge in the field of sampling metallic metallurgical materials appears to have been quite insufficient, and it is felt that when the principles involved are once thoroughly comprehended their universal application will be appreciated, so that it will make no difference whether pig iron or gold bullion is offered for test. It may further be noted that a discussion of the theories underlying practical methods is placed under the caption "Practical Sampling," with the idea that no one can be a practical sampler unless he is capable of analyzing his methods. No attempt has been made to advocate any one method, but it is hoped that the analyses of all of the methods in use will show where each may be correctly and safely applied. The fact that it is possible to demonstrate the theoretical correctness of several methods indicates the invalidity of the claim that any single one of them is the standard.

Jan 1, 1916

Another major aluminum company announced intentions to follow other domestic producers recent price actions by raising its unalloyed ingot quotes by 3¢ to 44¢ per pound, effective June 1, 1976. COBALT: All final data for 1975 are included in the table for cobalt on page 23. Demand in March increased significantly for the second month in a row, signaling a recovery from the previous year's relatively low demand levels. Imports of cobalt tripled in March over those of February. This should partially offset reduced sales of cobalt excesses from the National Stockpile. Import projections for the next several months have been lowered because transportation difficulties in Zaire are expected to result in reduced shipments.

Jan 1, 1976

By Walter E. Vanderpool

Three drilled foundations for an elevated water-tank were instrumented, tested and monitored during construction and the first two years in service. One shaft was load tested by the Osterberg method. A void was detected in one shaft by cross-hole sonic logging, pulse-echo logging and concrete coring. The void was instrumented, hydrostatically tested and pressure grouted. The shaft was ?abandoned? and replaced by two smaller shafts with a straddle beam cap. One of the replacement shafts and the cap were instrumented. The strain that appeared in the abandoned shaft, the replacement shaft and the cap were monitored during the remainder of the construction, through the commissioning test and the first two years of service. The results demonstrate the precision and sensitivity of the vibrating wire strain gage.

Jan 1, 2004

By K. Morsi

The interest in spark plasma sintering has been growing considerable over the past few years. This has been brought about by the unique advantages of the process, which include reduced sintering temperatures and times and the production of materials with unique microstructures and properties. Despite its current reputation as an outstanding process that has solved major problems such as nano-powder consolidation, it has so far been largely limited to the manufacture of simple shapes, due to its inherent geometric configuration. In this paper we present preliminary results on spark plasma "extrusion" that can allow the production of extended geometries via electric-current processing. Preliminary results on the processing and microstructure of spark plasma extruded aluminum are discussed.

Jan 1, 2009

By C. S. Wageman

Staying competitive in the highly aggressive Powder River Basin is a challenge facing all operators. Any advantage that a mine utilizes to improve productivity and reduce costs could mean the difference in the tight spot coal market. Technological advances in mining equipment and data acquisition at the Eagle Butte Mine in Gillette, Wyoming result in productivity gains and increased maintenance awareness. A new overburden haulage truck fleet with an onboard payload and fault monitoring system interacts via telemetry with the loading shovel and PC's located in production and maintenance offices, enabling staff to monitor production and maintenance on a real-time basis. This paper will describe the system and highlight the benefits realized as a result of its implementation.

Jan 1, 1996

Editor?s note: Each year, the June issue of Mining Engineering features an industrial minerals review. Several people put in a fair amount of time in developing the material for this issue, all the while doing their own jobs. Thank you to the industrial minerals annual review editor, to the Industrial Minerals and Aggregates Division technical committee chair and vice-chairs, and to the authors of the individual commodity profiles. Jim Norman, member SME, of Tetra Tech, is the industrial minerals annual review editor. Candace Trimble, member SME, of Oil-Dri Corporation of America, is chair of the Industrial Minerals and Aggregates Division?s Technical Committee.

Jan 1, 2012

By S. L. Chen

Keywords: copper, concentrate drying, steam dryer, dryers By placing additional demands on energy and gas flow, the moisture content of a copper concentrate has an adverse effect on the smelting process. Different drying technologies, such as directly heated rotary dryers, flash dryers, and steam dryers, are available to solve this problem. The energy requirements of and off-gas generated from different dryer types are compared. The performance of the steam dryer was found to be superior to that of the others. In particular, the rotary steam dryer and its benefits are discussed. Structural properties confer an advantage on the rotary steam dryer, for wear on tube elements is eliminated, and drying efficiency is improved. If steam is available, the rotary steam dryer is an excellent choice for drying copper concentrates.

Jan 1, 2006

The research described in this report was conducted under a cooperative research agreement between the U.S Bureau of Mines Twin Cities Research Center (TCRC), Cleveland-Cliffs Inc. (CCI), and three operations in Northern Michigan managed by CCI: the Empire and Tilden surface taconite mining operations, and the Central Shops maintenance facility. All of these operations are in or near Ishpeming, MI. The Human Factors Research Group at TCRC is responsible for designing, planning, and conducting the research, and reporting on the findings. This project was carried out in order to investigate the high prevalence of back injuries being experienced by workers employed at the three CCI Northern Michigan sites, In an analysis of Company accident records for workers employed at these sites, it was determined that back injury problems confronting the CCI sites mirror those confronting the entire mining industry.

Jan 1, 1994

The uptake of zinc, lead, and copper by the flora of the Tui Base Mine area near Te Aroha is described.Vegetation and soil samples were taken from two traverses across the Raukaka Lode. Results. after statistical analysis, indicated that Beilschmiedia tawa was a suitable species for biogeochemical prospecting for lead and that SchefJlera digitata was satisfactory for zinc.The tawa showed a negative anomaly for lead over the vein itself but not over the adjacent dispersion halo. It was concluded that lead concentrations greater than 230 p.p.m. in the wood ash of the tawa and zinc concentrationsgreater than 540 p.p.m. in the leaf ash of S. digitata denoted threshold values for anomalous mineralization in the soil beneath. Although both species contained copper, neither indicated a soil anomaly for this element.

Jan 1, 1969

By Jannie van Deventer

"Innovation in the minerals industry has been lagging behind comparable industries like oil and gas. An incremental innovation culture that tolerates long lead times between invention and adoption has been exacerbated by a research grant structure that inhibits radical idea generation. Entrepreneurs who can make the link between ore source, technology and finance will cause a shift in innovation culture and open up substantial opportunities in the minerals industry of the future. By extrapolating existing trends in technology within and outside mineral processing, a crystal ball vision of future innovation is shaped with the aim to lower energy and water demand, reduce CO2 emissions, decrease operating and capital costs, reduce environmental impact, and secure a social licence to operate. Advances in nanotechnology, advanced materials and biotechnology will impact mineral processing, but the initiative for technology transfer must come from mineral processors. Laminates of graphene oxide can offer efficient filtration and separation media, while microfluidic devices will be used for desalination, solvent extraction and analysis. Substantial progress is expected on benign lixiviants and separation agents, such as nanoscale supramolecular hosts that can serve as high-capacity, selective and recyclable ligands and sorbents, and solid aminobiphosphonate-based adsorbents. Radical ideas for the recovery of precious metals from non-assayable ores and the generation of energy above unity will be adopted in selected minerals projects. In-situ mining in which microbes generate lixiviants at mineral surfaces will simplify processing circuits. Specific ores will be subjected to microwave processing and electropulse liberation to enhance recovery. Ultrafine grinding using devices of low energy consumption will be done mainly dry, followed by dry separation. New flotation cells will remove efficiently either coarse particles or ultra-fine particles, with mineral surfaces being modified not just by new reagents but also by selective microbes. Innovation in mineral processing indeed has a bright future."

Jan 1, 2014

By Paul M. Hall

In the last several years, the coal mining industry has made significant changes in the design of longwall mining systems to make them more productive. Some changes, such as increasing the length of the coal faces and increasing the capacity of the face conveyors, have resulted in problems with achieving sufficient motor torque to start and operate the longwall face conveyors. Other changes, such as increasing the size and/or decreasing the percent impedance of longwall power center transformers, have resulted in problems with the short-circuit currents on the transformer secondaries exceeding the interrupting ratings of the molded case circuit breakers used to protect the secondary circuits. A survey of 24 longwall mining systems in northern West Virginia was conducted to investigate both problems. The results of the survey are presented and analyzed. Several recommended solutions to the problems are presented to enable the coal mining industry to design safe and productive longwall mining systems.

Jan 1, 1982

By Maurice Bottiau

The recent evolution of the piling market clearly shows a growing demand for screw piles with soil displacement. The recently developed Omega Screw pile ful-fill these new expectations, combining the advantages of vibration-free systems and the behaviour of a displacement pile. The paper describes recent experience and new applications with this very promissing pile. Full-scale load tests were carried out in different countries as U.K. or Sweden. A very attractive and innovative piled embankment is also described, using geogrids in order to transfer the loads from the superstructure to non-reinforced Omega-piles.

Jan 1, 1996

By Compiled by Staff

"INTRODUCTIONThe U.S. Bureau of Mines (USBM) was established in the public interest to conclude inquiries and scientific and technologic investigations on mining and the preparation, treatment, and utilization of mineral substances; to promote health and safety in the mineral industries; to conserve material resources and prevent their waste; to further economic development; to increaseee efficiency in the mining, metallurgical, quarrying, and other mineral industries; and to inquire into the economic conditions affecting those industries. The organic act of the Bureau, as amended by Congress and approved February 25, 1913, made it the province and duty of the U.S. Bureau of Mines to ""disseminate information concerning these subjects in such manner as will best carry out the purposes of this Act.""In accordance with this directive, USBM reports the findings of its research and investigations in its own series of publications and also in articles that: appear in scientific, technical, and trade journals; in "" proceedings of conventions and seminars; in' reference books; and in other non-USBM publications. The number of these reports, the wide range of subjects they cover, and the variety of mediums in which they appear make this kind of list both necessary and valuable.This edition describes reports and articles published during calendar years 1992 and 1993. It supplements the 50-year list of Bureau publications from July 1, 1910, to January 1, 196O 2; and these 5- year lists of publications and articles: from January 1, 1965, to December 31, 1969 4, from January 1, 1970,to December 31, 19745 , from January 1, 1975, to December 31, 1979 6 , from January 1, 1980, to December 31, 1984 7 , and from January 1, 1985, to December 31, 1989 8."

Jan 1, 1994

By Eric S. Weiss

The National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA) conducted joint research to evaluate explosion blast effects on typical U.S. mine ventilation stoppings in the NIOSH Pittsburgh Research Laboratory?s (PRL) Lake Lynn Experimental Mine (LLEM). An innovative Australian-designed brattice stop-ping was also evaluated. After mine explosion accidents, MSHA conducts investigations to determine the cause(s) as a means to prevent future occurrences. As part of these postexplosion investigations, the condition of underground stoppings, including the debris from damaged stoppings, is documented as evidence of the approximate strength and the direction of the explosion forces. The LLEM data showed that a typical dry-stacked and coated solid-concrete-block stopping survived a total explosion pressure of ~6.7 psi (~46 kPa) and was destroyed at a total explosion pressure of ~7.6 psi (~52 kPa). In comparison, a typical dry-stacked and coated hollow-core concrete block stopping survived a total explosion pressure of ~3.4?4.3 psi (~23?30 kPa) and was destroyed at a total explosion pressure of ~3.6?5.2 psi (~25?36 kPa), depending on the length of the pressure pulse and the value of the pressure-time integral. A typical steel panel stopping design survived a total explosion pressure of 0.8 psi (5.5 kPa) and failed at a total explosion pressure of 1.3 psi (9 kPa). The LLEM data also showed that an obstacle blocking the path of a pressure wave resulted in a higher reflected pressure at the obstacle. An 8-in (20-cm) thick wet-laid solid-concrete-block stopping coated on one side survived a total explosion pressure of ~26 psi (~180 kPa); this stopping was not tested to failure. A 6-in (15-cm) thick wet-laid solid-concrete-block stopping coated on one side survived a total explosion pressure of ~14 psi (~97 kPa) and was destroyed at a total explosion pressure of ~25 psi (~172 kPa). An innovative Australian woven cloth stopping survived an explosion pressure of 4.0 psi (27 kPa) and was destroyed at an explosion pressure of ~6.1 psi (~42 kPa). These results will help investigators determine the approximate explosion forces that destroy or damage stoppings during actual coal mine explosions.

Jan 1, 2008

By C. J. Van Treeck

PGE concentrations of 18 g/t occur in the pyroxene rich rocks at the Union Bay Alaskantype complex. This PGE enrichment is hosted in magnetite veins. These veins cross magmatic layering and have an irregular morphology in both outcrop and thin section. Fe-Ti oxide geothermometry suggests that this mineralization took place between ~700-400°C. A variation in the amount of ilmenite and Mg- Al spinel exsolution in magnetite correlates with temperature estimates, lower temperature magnetite has less exsolution. Hydrous silicates form an alteration envelope around magnetite veins with a formation temperature of <575oC, vary with temperature, and contain appreciable amounts of Cl. Interaction of a PGE-Fe-Cl rich fluid with clinopyroxene increased the fluids pH and decreased PGE and Fe solubility depositing a PGE enriched magnetite within the Pyroxenites and Olivine Pyroxenites of the Union Bay complex.

May 1, 2003

By J. R. Alldredge

This Bureau of Mines report presents a computer code that has been developed for describing and testing the statistical distribution of general continuous data sets. The statistical distributions used include the normal, lognormal, exponential, chi square, gamma, and uniform. Histograms for observed and expected values are plotted for each distribution. An example using geologic data obtained from a study of the geometric properties of natural fractures in oil shale rock illustrates the use of the computer program, GDIST.

Jan 1, 1977

By K. Muralidharan, P. R. Rao, M. Momayez, K. A. Runge

The evolution of trapped geothermal heat in hot underground mine along with emission of toxic gases and dust during mine activity makes the mine environment unfavorable is hazardous to worker’s health. This imposes significant demand on cooling and ventilation systems. As a result, substantial costs are incurred while implementing environmental regulation processes to dissipate the heat and provide comfortable working conditions. Thus, as an alternative, the development of cost effective materials to act as efficient thermal insulators is on the rise. Thermal conductivity is an important property that is a direct measure of a material’s ability to facilitate/deter heat flow. In addition to their superior chemical resistance, adequate mechanical strength, abrasion and fire retardant as well as environmental benefits in comparison to existing building materials such as ordinary Portland cement, aluminosilicate based geopolymers are now gaining widespread interest as promising thermally insulating and sustainable materials. This paper begins with an overview of geopolymers, transitioning into a discussion of recent developments in the field of geopolymer development as a thermally insulating material broadly classified into: filled geopolymers and porous geopolymers resulting in structures with enhanced ability to impede heat flow.

May 9, 2020