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By H. Walqui, S. K. Kawatra, C. H. N. Jeltema, T. C. Eisele

"The literature contains many cases where the shape of hydrocyclone efficiency curves vary from the ideal “S” shape. These often appear as changes in slope, or inflections. These inflections can be divided into two categories: “coarse” inflections, which are caused by differences in the density of the minerals being separated, and “fine” inflections, for which there are a number of competing hypotheses concerning their cause. The existing literature addresses either the fine inflection or the coarse inflection, but no studies have reported both types of inflection occurring at once in a single hydrocyclone test. This paper presents hydrocyclone results from both in-plant studies and laboratory experiments that show both coarse and fine inflections. The industrial significance of both types of inflections is discussed. Hydrocyclone efficiency curves show the probability of any given particle reporting to the hydrocyclone underflow as a function of its size. Selectivity functions, S(d), are used to represent the fraction of the feed material in size fraction “d” that reports to the hydrocyclone underflow. Plotting this selectivity function against particle size leads to the standard S-shaped efficiency curve shown in Fig. 1. In the “uncorrected” curve, the tail of the curve does not go through 0%, because a portion of the solids are bypassing classification. This happens as a result of their being carried along by the water, and is most important for the finest particles. The curve can be “corrected” based on the fraction of the feed water that reports to the underflow, represented by the bypass fraction, Rf. The corrected curve then normally passes through 0%, as shown in Fig. 1.The act of correcting the curve shifts the value of the d50 size, which is the size that has an equal probability of reporting to either the overflow or to the underflow. Correcting the curve to account for the bypass fraction makes it easier to compare cyclone performance under conditions that cause the quantity of water in the underflow to change, but that do not alter the actual corrected cut size (d50c).The corrected efficiency curve can be expressed closely by equations such as Plitt (1976):"

Jan 1, 2015

This paper presents the results of an experimental study undertaken to demonstrate the feasibility of using silica sand as a grinding media in stirred ball mills for ultra-fine coal grinding. Laboratory batch as well as bench scale continuous tests indicate that the use of silica sand can reduce the energy consumption by 50% and more over its steel media counter-part. Moreover, this approach has been found to eliminate the disadvantages observed with grinding using steel media such as high replacement cost, contamination of coal through media wear, greater degree of coal oxidation due to higher slurry temperature and greater level of noise dissipation. Additionally, coal-sand attrition system reduces the manpower time required which is often spent towards cleaning and storing of steel media in inert atmosphere to avoid rust and corrosion problems.

Jan 1, 1991

By T. E. Masoner

The struggle to get the minerals industry seriously interested in high intensity wet magnetic separation* has been difficult. The high capital cost of the equipment, the lack of basic research, the lack of operating information, and the diverse characteristics associated with different minerals and ores have prevented the development and use of HIMS-W on a wide scale. The Climax Molybdenum Company, a Division of American Metal Climax, Inc., located at Climax, Colorado, was among the first companies in the Americas in recent years to support the development of HIMS-W to recover weakly magnetic minerals on a large scale. The Climax Molybdenum Company, one of the world's largest underground mines, processes about 40,000 tons per day of ore, from which about fifty million pounds of molybdenum disulfide are produced each year. By-products include tungsten, iron pyrite, tin, and some monazite.

Jan 1, 1968

By Allan G. Provost

Shaft construction is assuming ever increasing importance when new mining enterprises are considered. The reasons for this increased emphasis is the much greater depths at which many new ore-bodies are being developed and the rapid depletion of near surface reserves requiring mines to go to greater depths on existing deposits. These greater depths increase the probability of exposure to unfavorable geologic conditions and it is more likely that high ground and/or water pressures will be experienced at these depths. The large capital costs involved and the critical position of a shaft in the overall mining program necessitate that this element of project development be given careful and critical consideration. The Henderson No. 2 Shaft is located in the Rocky Mountains of north central Colorado (See Figure I), about 55 miles west of Denver, near the community of Empire in Clear Creek County. At the 10, 442 foot collar elevation, winter arrives in late September and brings snow to contend with until May. The labor force for Shaft No. 2 is approximately 90 men. They are provided access to the project via all-weather U. S. Highway 40. SHAFT DESIGN The Henderson No. 2 Shaft is a 28-foot I. D. circular, concrete lined (1 foot thick) vertical shaft. The final depth will be approximately 3100 feet

Jan 1, 1972

By T. J. Lutz, D. S. Yantek, L. Yan, J. R. Srednicki, J. A. Yonkey, G. T. Homce

Federal regulations require the installation of refuge alternatives in underground coal mines. Of the inuse refuge alternatives, more than 95 percent are mobile refuge alternatives, with the remainder being built-in-place (BIP) refuge alternatives. Heat/humidity buildup has been one of the major concerns with mobile refuge alternatives. For BIP refuge alternatives, however, there is a lack of in-mine heat/humidity test data to determine the extent of heat and humidity buildup. To quantify heat/humidity buildup in BIP refuge alternatives, the U.S. National Institute for Occupational Safety and Health (NIOSH) performed a series of heat/humidity tests on a 60-person BIP refuge alternative with and without a borehole air supply. At various times during the year, tests were performed with cooled, heated or unconditioned borehole air to examine how various outdoor temperatures may affect the thermal conditions inside a BIP refuge alternative. The results show that the air supplied to a BIP refuge alternative may require heating or cooling, depending on the outside air temperatures and the temperature of the mine. For example, during tests with an external ambient temperature above 21 °C (70 °F) and a relative humidity of 90 percent, providing 13 °C (55 °F) dew point air at 775 scfm, which is slightly higher than the mandated flow rate of 12.5 scfm per person, kept the internal apparent temperature below the mandated 35 °C (95 °F). Results for each test case are presented.

Jan 1, 2018

By Yasushi Arai

"Among Tokyo Metro’s approximately 200km of subway lines, the Tozai Line that connects Chiba Prefecture and mid-Tokyo experiences congestion of up to 199% at worst and relief of this has become urgent. Therefore, as it is imperative to increase the number of trains operating in the exceptionally congested area from mid-Tokyo going east, a large-scale renovation work is planned between Iidabashi Station and Kudanshita Station that will facilitate turn-back via 3 tracks. While ensuring the safe and stable operation responsible for about 1.35 million passengers daily, this highly difficult work of inner wall demolition and reinforcement of the side walls and floor slabs will only be implemented for 3 hours during late night. This paper discusses large-scale plans to improve turn-back facilities, and the methods of construction therein as an example of operational improvement of a subway network. 1) INTRODUCTION The Tokyo Metro Tozai Line (“Tozai Line”) opened over the entire 30.8 km distance from Nakano to Nishi-funabashi on March 29, 1969. It has the longest operating length of the nine Tokyo Metro lines, and was the first subway line to extend past the borders of the Tokyo Metropolis. Through train services with two other railway companies are available from the Tozai Line. Tozai Line trains join the Sobu Line of the East Japan Railway Company (“JR East”) and the Toyo Rapid Railway Line of Toyo Rapid Railway (“TR”) from Nishi-funabashi Station, and the JR Chuo Line from Nakano Station. The line is structurally distinctive in that 51% of it was built using the open-cut method, 43% of it is elevated and the remaining 6% was built when we used the shield method for the first time 1)2)3)."

Jan 1, 2016

By Barnettm Ray R.

As a result of the Farmington explosion, the U. S. Bureau of Mines commissioned the National Academy of Engineering to a determine what steps could be taken in a short time frame to significantly reduce fatalities as a result of underground fire and explosion in coal mines. Three areas were named by the Academy as having the greatest potential; survival, communications, and rescue. The Bureau subsequently awarded a $3-5 million contract to the Special Systems Division of Westinghouse Electric Corporation for the development of prototype equipment and procedures. These were recently tested in a simulated emergency situation and will be delivered soon. Contractor recommendations for utilization and for further development effort will be studied and appropriate action taken.

Jan 1, 1971

Ferric (Fe3+) ions are omnipresent in flotation circuits. Depending on pH and the nature of the ore body, Fe3+ ions may play a role in the adsorption of thiol collectors on sulfide minerals. To investigate this possibility, a two-compartment galvanic coupling cell was designed. This cell was used to monitor changes in contact angle of a sulfide mineral in one compartment, while varying concentrations of the Fe3+ ions in the other. The results showed that Fe3+ ions promote xanthate adsorption as indicated by the increase in contact angle. Implications of this finding in sulfide mineral flotation in general will be discussed.

Jan 1, 1998

By T. M. Yegulalp

A short review of the current practice and recent developments is followed by a description of a newly developed approach for the solution of the optimum ultimate pit limit problem. The new approach utilizes the network modeling of the problem for solution by maximum flow algorithm. The latest developments in the implementation of maximum flow algorithm present significant time and memory savings as compared to initial development due to Ford and Fulkerson. Results of a series of computational tests are presented to demonstrate how this approach performs as compared to the well-known Lerchs Grossman algorithm. It is also shown that the solution by the new method will automatically include several optimal solutions based on predetermined number of benches to be included in the analysis.

Jan 1, 1993

By E. A. Gyawu, L. L. Eng, M. Fikru, K. Awuah-Offei

Investors and other stakeholders are increasingly concerned about the quality and quantity of sustainability disclosures as well as the extent to which such disclosures correlate with sustainability practices of mining firms. This is because disclosure policies vary widely across firms in terms of extensiveness, materiality, and disclosed topic. In this paper, we conduct a preliminary examination of the relationship between sustainability performance and disclosure. We use sustainability performance indicators such as water and energy use and the Sustainability Accounting Standards Board’s (SASB’s) standards to evaluate disclosures. Our preliminary results show that some measures of sustainability performance (energy use) are negatively correlated to the amount and quality of disclosures while others (water use) are not. Thus, investors should not judge sustainability performance based solely on the amount and quality of sustainability disclosures. In addition, our results suggest that firm size and ownership as well as institutional membership could impact the strength of correlations between disclosure policy and sustainability performance

Mar 2, 2022

By Fu Lizhu, Qiu Tingsheng

An application of water-system magnetizing technology for the mineral processing and hydrometallurgy is introduced in this paper. The water-system magnetizing technique flotation and cyanidation leaching test of vein-ore of gold-bearing and conventional technique flotation and cyanidation leaching of gold-bearing vein-ore was carried out. The best condition of water-system magnetizing was determined by orthogonal test. The results have shown that the water-system magnetizing technology may increase the efficiency of flotation and cyanidation leaching for gold. The industry-scale test results also show that it can increase flotation recovery by 1-3% and leaching extraction by 3-5% of a gold-bearing vein- ore. The interaction of magnetizing water-system with minerals was carried out and initially investigated.

Jan 1, 1995

By F. G. Miller

Over the past 30 years, the coal industry has been continually striving to perfect methods for cleaning fine coal to acceptable ash and sulfur contents while maintaining maximum product yield. The flotation process has been part of this effort and its importance is expected to grow as new utilization technology demands finer and purer coal products. The work outlined in this paper is part of a larger effort aimed at development of new and improved flotation systems for removing sulfur and ash from as-mined coal as well as for producing super-clean coal for future markets. The concepts and data presented are now serving as a basis for designing fine-coal circuits in which improved efficiency is obtained by optimum use of flotation.

Jan 1, 1986

By Dale S. Preece

INTRODUCTION The Waste Isolation Pilot Plant (WIPP) is a research facility located in Southeastern New Mexico. The WIPP is being developed by the U. S. Department of Energy (DOE) to demonstrate the safe storage of defense-related radioactive wastes in bedded salt. Since the WIPP is a research facility. a number of large-scale in situ experiments have been planned and are currently under construction (Munson, 1983). These experiments were designed to study various aspects of nuclear waste storage in bedded salt such as mechanical responses and creep closures of drifts, thermal response due to heated canisters, and thermally-induced fluid migration. One purpose of the WIPP is to develop and demonstrate a general predictive structural analysis capability for a bedded salt repository. One set of experiments, called the Geomechanical Evaluation (Room G), is heavily instrumented to study the creep around several rooms with different configuration. A Layout of the Geomechanical Evaluation room is shown in Figure 1. One portion of it consists of wedge shaped pillar where two drifts intersect at an angle of 7.5 degrees. The pillar can be seen at the bottom of Figure 1. One purpose of the wedge pillar experiment is to study progressive pillar failure in the tip region. Another is to determine how nonuniform pillar thickness affects creep closure of the drifts. An important aspect of the experiments is the correlation between experimental data and corresponding pretest finite element analyses of the site. The finite element simulations serve two purposes. First, the computer simulations aid in understanding the experimental results by providing calculated stress. strain and displacement fields that cannot be measured directly. Second, comparison of calculated and measured drift closures serves as a method for validating or improving the finite element models and the constitutive models employed. The wedge pillar geometry required a 3-D finite element creep calculation. Results from these 3-D calculations will be presented in this paper. A 2-D plane strain double drift model which approximates the wedge pillar geometry at a slice perpendicular to the drift has also been performed and will be compared to the 3-D results in this paper. FINITE ELEMENT COMPUTER PROGRAMS Two finite element computer programs. JAC (Biffle, 1984) and JAC3D (Biffle. 1986), were used. JAC is a 2-D finite element program developed for quasi-static analysis of non-linear solids. It employs the conjugate gradient iterative technique to obtain a solution Spatial integration is performed using a single gauss point in each four node quadrilateral element. An hourglass viscosity technique is used to control the zero energy modes that occur with single point integration. The single point integration combined with the explicit nature of the program and exploitation of CRAY-1 computer architecture results in very efficient execution J4: results were compared to results obtained with eight other 2-D structural creep computer codes in the second WIPP benchmark exercise (Morgan, 1981) JAC3D was derived from JAC to treat 3-D finite element models and has many of the same characteristics including single point integration and hourglass viscosity. These characteristics have made 3-D creep analyses more reasonable by significantly reducing computation time The first exercise of the creep capability

Jan 1, 1986

By Robert A. Cummings

Disintegration of the immediate shale roof in coal mines interferes with ventilation, production, and safety. The effect is seasonal and correlates with high levels of moisture in the intake ventilation air. Disintegration, though not completely understood, is caused by shale dilation and weakening upon exposure to atmospheric moisture. Fluctuating moisture conditions are particularly deleterious, and may be at least partially controlled by "tempering" the air before it is brought to the working places. Roof behavior was studied in an operating mine during a 12-month monitoring period. This approach can be used in developing criteria to reduce or prevent shale roof deterioration.

Jan 1, 1981

By William Detty

An architect representing the Atlanta office of the Brick Institute of America periodically presents a slide lecture to interested groups entitled "The First 10,000 Years of Brick". The title signifies the fact that brick, man's oldest manufactured building material, has been around for quite some time and will continue to be utilized by architects and builders in the foreseeable future. This is not to say that the brick industry can rest on its laurels and ignore the competition presented by newer more innovative products. The industry will have to be equally inovative and market oriented in order to maintain its market share of the predicted construction boom between now and the year 2000. The implication is made, however, that brick can be produced under rudimentary conditions and that the desire to use the product has been long standing. In addition, history has sham that there has been plentiful clay available to produce the product. This paper is an attempt to assess the climate in which the brick industry will operate during the next 26 years. An analysis of regulatory conditions affecting the manufacture of the product will be followed by an assessment of the materials environment in which the industry will be operating. These factors are then reconciled with a projected demand for the product to determine the ability of the industry to satisfy future demand for brick. From a mineral point of view this paper will address itself generally to the availability of and demand for clay. However, other than a brief overview of the uses of other specific types of clay, it will concentrate on the clays utilized in the production of structural clay products, specifically brick.

Jan 1, 1974

By John J. Reed

Since the beginnings of, the human struggle for survival and improvement, mining has been one of the basic endeavors of life. Until relatively recent times it was classed as an art. Now we are at work trying to, raise mining to the level of an engineering science where it belongs if we are to prosper. It should be self-evident that this goal can be attained only through industrial progress: based on education and research. It is true that our industry, left to itself, will develop a few new ideas and techniques through the years. However, we mining' engineers are relatively few in number compared to the other disciplines, and the rate of our improvement by such "accidental" discoveries is simply tooslow to keep pace with the rest of our technical civilization. It will be evident in the remarks that follow, that the rapid development of mining education, research, and the industry are extremely interdependent, and will be largely controlled by the amount of cooperation, support, and cross-fertilization that can be developed among all three.

Jan 1, 1961

By Homer E. Harris

As a result of the enactment of the Federal. Coal Mine Health and Safety Act of 1969 1, the Department of Health, Education, and Welfare (HEW) has been carrying out research in the "field of coal mine health". The National Institute (formerly Bureau) for Occupational Safety and Health (NIOSH) was designated the agency within HEW to be responsible for such research activities. One of the early programs sponsored by NIOSH was undertaken by Eastern Associated Coal Corp., with the Harvard University School of Public Health participating as a subcontractor to Eastern. This program on Coal Mine Respiratory Protective Devices, which started on June 30, 1970, had five major objectives as follows: a. to determine current status of respirator usage with respect to duration and frequency, types. and maintenance b. to determine acceptability ( and reasons therefor) of currently used units c. to determine protection factors provided by respirators worn by working miners d. to make recommendations on ways to improve existing units, or on research needed to develop new types of respiratory protective devices for coal miners e. to provide recommendations to mine management on more effective use of respiratory protective devices

Jan 1, 1973

By Xinyang Wang

It is believed that sulfur and volatile matter con-tents in coals are the main intrinsic properties to cause the self-heating of coal. Their oxidation at lower temperatures than that of fixed carbon to initiate coal's self-heating should be quantified. This study is aimed to improve the previous mathematical model developed by the authors for studying the coal's propensity for spontaneous combustion. It enhances the model's ability to consider the effects of sulfur, volatile matter and moisture contents in the coal three important factors affecting the coal's self-heating process. Sulfur exists in coal primarily in the form of pyrite which will be oxidized rapidly under suitable conditions. Volatile matters, higher in low rank coals, are more easily to be oxidized. Heat of water condensation provides initial energy for low temperature oxidation. Heat release rates for pyrite oxidation and moisture condensation are built in the model. Finally, the simulation results in terms of time versus temperature on pyrite oxidation and moisture condensation are validated with the adiabatic testing data respectively.

Jan 1, 2013

By K. C. Ko

The pit slope angle dictates the economics as much as the depth of the pit. Steeper slope provides more ore reserves, at the same time, the steeper slope presents higher probability of instability and associated maintenance problems. While large open pit mines mostly belonged to nonferrous metals in the past, other mines are becoming deeper as the mine economics permits deeper mine operations, Such minerals include coal, uranium, phosphate, and others. There are some basic differences between an open pit slope and slopes that are encountered in usual civil engineering work such as dam embankments and highway cuts (Figure 1). The stability of the civil engineering slope changes continuously with time due to ground-water movements, weathering, etc. But the stability of the open pit slope (Figure 2) changes more drastically day-to-day or even hour-to-hour, These changes occur because not only is the slope geometry being continuously changed by the mining operation, but also different geology and geologic structures are being exposed on the slope. Even when a particular slope area is not presently being mined, excavation in adjacent areas can affect the general condition of that slope area. A pit will experience some slope failures during its life.

Jan 1, 1977

By J. Noll, C. DeGennaro, C. Zhou, J. Srednicki

"The personal dust monitor (PDM) (model PDM3700), as well as other electronic devices, can cause electromagnetic interference (EMI) which can disrupt the operation of some proximity detection systems (PDSs). A 15 cm (6 inch) minimum separation distance between the miner-wearable component (MWC) of the PDS and the electronic device usually avoids these disruptions, but due to the amount of equipment on a miner’s belt and the method of wearing the PDM in some situations, this distance can be difficult to always reliably maintain. Another method of reducing EMI effects is utilizing magnetic field shielding. The shielding capability of several different materials was investigated by surrounding the PDM with the material and quantifying the EMI. A copper mesh pouch reduced the EMI from a PDM3700, allowing a minimum separation distance of 10 cm (4 inches) instead of 15 cm (6 inches) as shown in a previous study for an unshielded PDM. A MU-metal box had a better shielding effectiveness, as it further reduced the minimum separation distance to less than 7 cm (2.8 inches). Shielding reduced the EMI of the PDM with MU-metal providing better results than the copper mesh. These materials may be beneficial for shielding individual components of the PDM or for constructing a shielded pouch. However, before the advantages of a shielded pouch can be determined, the effects of just the shielding material (metal) on the PDS needs to be quantified. INTRODUCTION According to statistics from the Mine Safety and Health Administration (MSHA), 43 miners have been fatally struck or pinned by a continuous mining machine (CMM) since 1984. In an effort to prevent future striking and pinning fatalities from occurring, proximity detection systems (PDSs) have been developed and are required on all operating CMMs in underground coal mines, with the exception of full-face CMMs, by 2018 (MSHA, 2015)."

Jan 1, 2018