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By R. E. J. Putman

Rising demand, artificial market conditions, increased overseas competition, and a fluctuating international situation have brought ever increasing pressures to bear on the nonferrous metals industries, and particularly in the United States, Although capacity is being expanded by the construction of new plants and the development of new ore deposits, increasing attention is being focused on the possibilities of improving the performance of the existing installations and of getting the most out of the new equipment now installed. At first sight the task appears formidable. Based on raw materials which are nonhomogeneous, and possessing characteristics which are hard to quantify, even the processes by which the values in the ores are concentrated and extracted are in many cases not fully understood. The necessary analytical equipment and transducers demanded by these industries have also been slow in development and their earlier absence has hampered the application of modern control technology, This is reflected in plants which have been designed for ease of manual rather than automatic control, and in which the application of control techniques at first sight appears economically prohibitive. However, in any industry progress often comes only in small steps, It may be that by the wise choice of limited objectives and perhaps only partial solutions, substantial improvements in plant performance can be implemented now, and with only a modest investment. If modern control equipment is chosen of the type which can be reprogrammed, advantage can be taken later of more sophisticated solutions as the technology of the industry advances. This task of improving plant performance can and must be commenced even though our knowledge is incomplete. The experience of a related mineral consuming industry, with similar problems in the past, can be encouraging.

Jan 1, 1967

By Cheryl L. Mardock, Michael D. Strickler

The Bureau of Mines is examining mineral deposits bearing strategic elements such as cobalt, for which the United States heavily relies on imports. The Turner-Albright volcanogenic sulfide deposit in southwestern Oregon is marginally economic based on its gold content and associated silver, copper, zinc, and cobalt values. Bureau research on the Turner-Albright deposit was performed (1) to evaluate domestic cobalt recovery as a byproduct of gold production from massive sulfide ores; (2) to develop an analogue of modern sea-floor polymetallic deposits to determine the economic potential of the deep-sea resources; and (3) to compile information on the geochemistry and genesis of the deposit that can aid in future onshore exploration. Cold was introduced as near micrometer-sized disseminations by exhalative hydrothermal fluids near sea-floor vent sites and by late influxes of mineralizing fluids into lower zones of brecciated sulfides and basaltic fragments. Cobalt is a substitutional element in pyrite that occurs in outlying halos around original vent sites. Mineralogic studies conducted with a scanning-electron microscope and an electron microprobe determined that none of the ore minerals are amenable to traditional beneficiation methods such as gravity and flotation. An experimental oxygen pressure-leaching procedure developed by the Bureau has proven successful in treating such complex ores.

Jan 1, 1990

By Kenneth A. Pietila

The thickening and dewatering characteristics of refuse slurries are as variable as the coal mining operations and preparation plants that create them. This paper discusses these characteristics based on field studies at a number of mine sites. The connection between bench and full scale performance is confirmed with the design, construction and operation of an integrated 18m (60 ft) diameter thickener and 2.5 meter belt filter press system in Western Kentucky. The data from this system are presented.

Jan 1, 1984

The criteria used to design, operate and control flotation columns are significantly different from those used for conventional flotation machines. Therefore, a computer-aided design (CAD) package for column flotation has been developed. The simulator has been set up using guidelines developed at Virginia Tech and information published in literature during the past few years. The simulator is useful for determining the proper design and appropriate operating conditions for a column cell to fit a specific set of conditions. In addition, the simulator can be used for training in column operation and for trouble-shooting operational problems. Simulation results have been found to be in good agreement with experimental data obtained using laboratory columns.

Jan 1, 1990

By Harold Potter

(1) A great deal of experimentation has been carried out by the Wet Process Cement Manufacturers in connection with additives which make possible the production of a pumpable slurry at reduced moisture contents. We ourselves have made dozens of tests both at Laramie, Wyoming and Monolith, California. (2) The viscosity or pumpability of a slurry at a definite moisture content and fineness seems to depend on two basic phenomena. One is the physical structure of the raw material itself, which on fine grinding may or may not be excessively hydrophilic (water adsorptive). Usually crystaline or glassy raw materials are non- hydrophilic. The fine grained amorphous raw materials such as shales and clayey limestones very frequently are, however. (3) The second basic phenomenon affecting the hydrophilic tendencies of the raw material is the presence of certain soluble salts, especially gypsum and small amounts of alkalin carbonates or oxides. (4) Various soaps, and phosphates can be used to produce a pumpable slurry of low moisture content when using hydrophilic raw materials as well as can other proprietary materials such as certain long chain carbon compounds. Too frequently however, the price of such additives in conjunction with the amount required prohibits their use in the cement industry.

Jan 1, 1959

By R. K. Agarwal

In this paper a simple three-layered medium is considered. A circular hole is centrally located in the intermediate layer. The layered sheet is loaded uniaxially perpendicular to the stratification. The Young's modulus of the intermediate layer is lower than that of the outer layers. The stress distribution around the circular hole in a stratified medium is significantly different when compared to the case of a continuous homogeneous medium. The distribution depends upon the ratio of the height of [the] intermediate layer and [the] hole diameter. A comparison of stress the distribution and procedures for preparation and testing of [the] model are given. The potential of the technique is outlined.

Jan 1, 1968

By R. N. Gow

EH-pH diagrams are useful tools in understanding how mineral surfaces react in solution and particularly how aqueous conditions can be changed to enhance mineral leaching processes. However, successful application of these diagrams requires several things be kept in mind to prevent what others have termed ?gross errors? in their calculation and use. The aqueous Cu-S system is used as the basis for explaining the mass-balanced method of calculating EH-pH diagrams with the thermodynamic equilibrium software, STABCAL. This includes a breakdown of the Gibbs? Phase Rule and how it is employed in STABCAL to modify the diagrams. This methodology was then applied to the aqueous Cu-As-S system and resulting diagrams are compared against examples of those generated using the predominant-ion method. The resulting mass-balanced diagram for enargite (Cu3AsS4) is noted to compare well with spectroelectrochemical measurements using Raman spectroscopy and cyclic voltammetry.

Feb 23, 2014

By John D. Nelson

Unprotected uranium mill tailings impoundments can pose a significant risk to nearby inhabitants and the surrounding environment in the event of a prolonged or catastrophic release of contaminants contained in the tailings. As a result of this potential, reclamation plans for such facilities must include engineering designs to protect against disruption of the tailings and the potential release of radioactive materials. The goals for such engineering designs should be to provide overall site stability for long-term periods with no need for planned ongoing maintenance and to provide a repository for the tailings that will not place a burden on future generations. Although the goal is to provide a maintenance-free system that does not require monitoring, it must be recognized that some period of surveillance would be reasonable. The surveillance period could be relatively short and only needs to assure with reasonable confidence that the reclamation scheme that was implemented is functioning adequately. An investigation was conducted by Nelson, Volpe, Wardwell, Schumm and Staub (1983) entitled Design Considerations for Long-Term Stabilization of Uranium Mill Tailings Impoundments (NUREG/CR-3397). This report assesses the degree of confidence with which long-term reclamation plans can be expected to remain effective over specific periods of time, and to assess the additional effort required to extend the design period from one long-term period to a longer one. This paper presents a summary of that investigation and discusses some of the important conclusions.

Jan 1, 1984

By R. C. Bunge

The success of a mineral separation is commonly assessed from the separation curve, a graph of the recoveries achieved versus the corresponding separator settings. Two values characterize the curve, first the "splitpoint" which is the separator setting that produces a recovery of 50%, and second a measure for the separation sharpness. The splitpoint represents the "mean" while the measure for the separation sharpness represents the "scatter". In modelling the performance of crossflow separations the mean particle behavior is calculated from the force equilibrium that determines the particle trajectory which leads to a deterministic model. The scatter is then represented by a stochastic model. This presentation discusses the modeling of a crossflow separation and some implications with separation theory. The model is shown to successfully predict the performance of a magnetogravimetric separator.

Jan 1, 1992

By R. E. Krauss

The McLaughlin Mine is a world class epithermal gold deposit located in the coastal thrust fault of Northern California, U.S.A. Homestake adopted a proactive strategy in the permitting of the Mine. Extensive environmental base line studies were undertaken. Engineering and process alternatives were evaluated for environmental impact along with other factors. A unique pressure oxidation process was selected. Screening studies were conducted as a basis for the selection of waste rock and tailings disposal sites. Project engineering and permitting were fast tracked. Construction required eighteen months and the first gold bar was poured in Parch of 1985, six years after the initial discovery. Project facilities are designed and operated so as to minimize environmental impacts. A comprehensive monitering program demonstrates permit compliance. Reclamation of the site is ongoing throughout the Mine?s twenty year life. Non-mined lands are managed to maximize wildlife habitat value.

Jan 1, 1990

By G. A. Gruber

A flotation process has been developed to successfully treat ore from the Santo Domingo phosphate deposit in Baja California Sur. The ore contained less than four percent P205 with quartz, silicates, and carbonates as gangue minerals. Flotation of the low grade feed In sea water required that the conventioinal Crago Process, comprising direct anionic flotation, deolling, and inverse cationic flotation be augmented by an anionic cleaner flotation step, phosphate depression, and a calcite flotation step.

Jan 1, 1986

By Erik S. Bernard

"INTRODUCTION Reinforced Concrete (RC) members such as beams and columns are usually required to include stirrups to maintain post-crack shear capacity, and some may include stirrups that act as confining steel to maintain structural integrity during a seismic event (eg. NZS3101, ACI 318). To achieve seismic resistance, the spacing between stirrups is usually required to be much closer than is ordinarily prescribed for non-seismically resistant structures. Each stirrup must also fully enclose the longitudinal reinforcement with long end-hooks to ensure that the contained concrete is sufficiently restrained during reverse-cycle loading and the reinforcing bars are confined to prevent buckling. The close spacing between stirrups can lead to congestion of reinforcement within members, and can also be expensive to construct due to the labor-intensive nature of steel fixing. A possible alternative to closely-spaced stirrups is the use of fibers to provide restraint and confinement during a seismic event, although this is not yet recognized in codes. Previous experimental research (Jiuru et al, 1992; Filiatrault et al, 1995; Bayasi and Gebman, 2002; Billington and Yoon, 2004) has demonstrated that steel fibers are relatively effective in this application, but suffer the problem that their stiffness can make them difficult to consolidate within an already tight reinforcement cage, especially if they are relatively long (>40 mm). Moreover, steel fiber reinforced concrete (SFRC) is subject to embrittlement with the passage of time, leading to a steady loss of ductility beyond crack widths of 1-2 mm (Banthia and Trottier, 1994; Bernard and Hanke, 2002; Bernard, 2014; Bjontegaard et al, 2014; Bernard, 2015). Since cracks during seismic events are generally much larger than this, embrittlement may present a challenge to the long-term efficacy of SFRC during seismic events. An alternative to steel fibers for enhancement of seismic resistance is the use of macro-synthetic fibers. This type of fiber usually offers the advantage of being flexible so that consolidation is easier between reinforcing bars. They also offer superior durability compared to steel fibers and can reduce flexural crack widths (Bernard, 2016). Several recent small-scale investigations (Ma et al, 2012; Carnovale, 2012; Osorio et al, 2014) have indicated that macro-synthetic fibers can produce meaningful improvements in seismic resistance if used in combination with conventional steel reinforcing bars. The present investigation has extended research in this field by examining whether embossed macro-synthetic fibers can be used to increase the spacing between stirrups while maintaining seismic resistance."

Jan 1, 2016

By Richard L. Ash

Less than optimum production in mining always results when poorly blasted material is provided at loading points. More often than not the cause is due to blasting founds that fail to fully control and utilize explosive energy. In many cases the problem exists because too few blasters understand how blastholes actually break rock and recognize that blasting is a three-dimensional process in designing their blasts. To better understand how blasts can be more effectively designed the two major rock breakage processes are described. In addition, the respective contributions of the borehole and detonation pressures are defined as are the specific roles of the several important blasting design variables. The concept of stiffness as an engineering principle and its significance in blasting design is introduced for explaining the breakup of rock. Basic guidelines for affecting control over fragmentation and side effects like over-break are offered.

Jan 1, 1975

By Lynn B. Hales

Unfortunately, the term "control" has a negative connotation in the minds of many of our operating plant personnel. Whereas the opposite is true of those associated with research and technical centers in our industry. The magnitude of this difference in opinion and actual experience has often proved to be a major factor influencing the success or failure of process control applications. Through the years, many plant people have endured a number of unsuccessful attempts by "outside" people to "optimize" their plants; and these experiences have proved to have had quite a callousing effect on them. On the other hand, in many plants, successful process control efforts have made firm allies of the operating personnel, and have increased the number of metallurgical people who are well qualified and experienced in process control. The instrumentation industry, computer industry, and the mining industry's ability to quantify what is really happening in our processes have grown and developed rapidly since the first control efforts were made in the 1930's (1). Because of this-,: new control opportunities are becoming increasingly more feasible and older well established ones are becoming even more practical and necessary with regard to the economic s of our industry.

Jan 1, 1979

By S. Chander

The mechanism of oxidation of sulfur in pyrite is a function of the rate and driving force for oxidation. New evidence is presented in this article to show that at moderate potentials, a sulfur-rich hydrophobic layer is formed. Under ordinary conditions, the sulfur layer is covered with a layer of iron oxides, hydroxides, sulfate or oxy-sulfide ions. Under these conditions, pyrite is hydrophilic. In the presence of iron-chelating agents or iron sequestering ions, iron layer might not form. Under these conditions, sulfur-layer is exposed and pyritic might become hydrophobic. Stronger oxidizing conditions decompose the sulfur-layer, thereby making the surface hydrophilic.

Jan 1, 1992

By John A. Wolfe

Applications of mathematical statistics to the field of exploration are still relatively new. There are two primary reasons why little has been published in this field. First, if one discovers an effective technique for exploration, he does not like to disclose it. Second, the geologist needs to work closely with a mathematical statistician, and the communications barrier between the disciplines is formidable. The authors of this paper, one a geologist and the other a statistician, were interested in the economic benefit which appeared to be possible in the interdisciplinary area which they have called "geostatistics." An actual example has been selected to illustrate this benefit.

Jan 1, 1962

By B. K. Cantrell

A miner working in an underground coal mine with diesel equipment is exposed to a wide array of pollutants from the diesel exhaust. These include CO, CO2, NO, NO2, SO2, diesel-exhaust aerosol, and a variety of hydrocarbon compounds. A quantitative definition of the health risk resulting from these exposures remains elusive, but during the past several years, progress has been made in defining the problem. Results from epidemiological studies by Garshick, et al. (1988); animal inhalation studies by Mauderly, et al. (1986); Iwai, et al. (1986); and Brightwell, et al. (1986); and in vitro studies by Lewtas, et al. (1986), have provided sufficient data for the National Institute of Occupational Safety and Health (NIOSH) to recommend that "whole diesel exhaust be regarded as a 'potential occupational carcinogen,' as defined in the Cancer Policy of the Occupational Safety and Health Administration," NIOSH (1988). NIOSH further stated that "though the excess risk of cancer in diesel-exhaust-exposed workers has not been quantitatively estimated, it is logical to assume that reduction in exposure to diesel exhaust in the workplace would reduce the excess risk."

Jan 1, 1990

By QINGXIANG CAI, Lin Li, PENG LIU, IZHAR MITHAL JISKANI, XIANG LU, Wei Zhou, YONGLI ZHOU

The concept of green mining is to improve the mining industry in a holistic way so that it is safe, efficient, and environmentally sustainable. The purpose of this study was to develop an evaluation index system of green surface mining based on the theory of green grades. The evaluation model is comprised of three attributes (safety, efficiency, and environment), nine criteria, and 35 indicators. The fuzzy comprehensive evaluation method was used to determine the weights of indicators by taking into consideration degree centrality, closeness centrality, and betweenness centrality. Findings indicate that the environment is the most critical aspect of green surface mining, followed by efficiency and safety. The top five ranked green mining success indicators were the application of new technology, starting-off-rate of equipment, science and technology input to total investment, the number of accidents (decreased), and the production (increased). It was observed that more improvements are needed to overcome water, air, waste, and sound pollution. Attention should also be paid to land reclamation and post-mining land uses, which are key factors in green mining. The proposed model can be applied to evaluate and improve the level of green surface mining in other regions. This study provides a tool for decision-makers that can offer technical assistance to green mining.

May 26, 2020

By Peter G. Chamberlain

Domestic mining will not produce a significant portion of the manganese consumed in the United States unless new mining and processing techniques are implemented that will enable domestic lean ores to economically compete with rich foreign ores. One mining-processing technique that appears promising for certain deposits is in situ and/or heap leaching with aqueous SO2. Since leaching offers economic advantages of low capital costs, low operating costs, and short start-up times as well as environmental and safety improvements over conventional mining-processing, the Bureau of Mines studied the leachability of manganese deposits from several districts. Manganese oxides, hydroxides, and carbonates were leached to 80 to 90 pct recovery in 7 to 40 days of leaching with a solution containing 5 pct SO2 in column leaching tests. Preliminary cost analyses of surface mining-heap leaching, block caving-in situ leaching, and shrinkage stoping-in situ leaching indicate that the products of manganese leaching may be economically produced for the chemical and electrolytic manganese industries. The easiest marketable product to obtain would be a manganese sulfate commonly used as a fertilizer amendment. Manganese carbonates and hydroxides could also be precipitated from the pregnant leach solutions.

Jan 1, 1983

By A. Balint

The Photometric Optical Separation process is introduced and examples of sorting machines are given. Applications of the process are outlined in general terms with reference to specific types of industrial installations. Brief description is given of the capabilities and limitations of available equipment, including cost estimates.

Jan 1, 1967