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By T. Grounds, K. Singh, W. R. Reed, R. Cross, G. Ross, S. Klima, M. Shahan

"A 2nd generation roof bolter canopy air curtain (CAC) design was tested by National Institute for Occupational Safety and Health (NIOSH) at a Midwestern underground coal mine. During the study, the roof bolter never operated downwind of the continuous miner. Using a combination of personal Data Rams (pDR) and gravimetric samplers, the dust control efficiency of the roof bolter CAC was ascertained. Performance evaluation was determined using three methods: (1) comparing roof bolter operator concentrations underneath the CAC to roof bolter concentrations outside the CAC, (2) comparing roof bolter operator concentrations underneath the CAC to the concentrations at the rear of the bolter, and finally, (3) using the gravimetric data directly underneath the CAC to correct roof bolter operator concentrations underneath the CAC and comparing them to the concentrations at the rear of the bolter. Method 1 dust control efficiencies ranged from -53.9% to 60.4%. Method 2 efficiencies ranged from -150.5% to 52.2%, and Method 3 efficiencies ranged from 40.7% to 91%. Reasons for negative and low dust control efficiencies are provided in this paper and include: incorrect sampling locations, large distance between CAC and operator, and contamination of intake air from line curtain. Low dust concentrations encountered during the testing made it difficult to discern whether differences in concentrations were due to the CAC or due to variances inherent in experimental dust measurement. However, the analyses, especially the Method 3 analysis, show that the CAC can be an effective dust control device. INTRODUCTION Canopy air curtains (CAC) have been shown to be an effective respirable coal mine dust control for roof bolters in a laboratory setting with dust control efficiencies ranging from 14% up to 75% [Goodman and Organiscak 2001, Listak and Beck 2012, Reed et al. 2017]. Unfortunately, there is limited information on their effectiveness for controlling respirable coal mine dust in the field. On continuous miners, CAC dust control efficiencies ranged from 23% to 69% [Krisko 1975]. Two underground tests of the CAC on roof bolters demonstrated dust control efficiencies of 35% and 53% [Listak and Beck 2012] before problems occurred with operation of the CAC. Since the implementation of the new respirable coal mine dust limit from 2.0 mg/m3 to 1.5 mg/m3 (Code of Federal Regulations, 30 CFR 70.100, 2015), roof bolter CACs are becoming more commonplace in underground coal mines as a dust control tool to prevent roof bolter operator overexposure to respirable coal mine dust. J.H. Fletcher & Co. has been instrumental in delivering an effective design which incorporates the filter, blower, and canopy plenum seamlessly into the design of the roof bolter, resulting in a successful operational roof bolter CAC."

Jan 1, 2018

By H. G. Wickes

Virtually all fluorine consumed by the aluminum industry is as the electrolyte of the Hall-Heroult process for producing primary aluminum. A small amount of fluorspar is used but most fluorine is consumed as either aluminum fluoride or cryolite. Some fluorine- containing materials are used in secondary aluminum production, but the amount is negligible compared with primary production requirements. Any analysis of the future of the primary aluminum industry must take into account two powerful and closely related driving forces which are shaping that future. These factors are increasingly stringent restrictions on the emission of pollutants and the continuing cost-price squeeze. Nowhere do these factors combine more forcefully than in the area of fluorine consumption. We can safely assume that industry efforts to reduce fluorine consumption will be intensified and that these efforts will be fruitful. This paper will attempt to identify and quantify the factors and trends of fluorine consumption during the next decade. We will be concerned primarily with the demand for new fluorine. Sources of new fluorine will not be treated.

Jan 1, 1973

By W. Petruk

Mineral liberations that would be obtained by grinding an ore to a specific size can be predicted by analyzing unbroken ore pieces, and mineral liberations in ground ores and mill products can be determined directly by image analysis. Predictions of mineral liberations are made by measuring size distributions and textures of mineral grains by image analysis, and using liberation models. Ground ores and mill products are analyzed to determine the proportion of mineral that is liberated, and the data are used to evaluate mineral behaviour during mineral beneficiation. The liberation data for minerals in a suite of mill products from a circuit are processed by a materials balancing technique to calculate recoveries of minerals in different types of particles throughout the circuit. The liberation-materials balance data define mineral recoveries; define the behaviour of an ore in a concentrator, pilot plant or bench test; and indicate whether recovery improvements are possible and/or feasible.

Jan 1, 1991

By P. Massacci

The modelling of phenomena by nonlinear dynamic Systems Theory representations require the specification and identification of suitable models of the phenomenon and the availability of good optimization algorithms to determine the optimal controls. Stochastic disturbances and difficulties of monitoring the process lead invariably, otherwise, to suboptimal performance. It will be shown that an algorithm can be formulated which will simultaneously identify and optimize such a system. The properties of the algorithm will be derived and its convergence to an optimal control proved. Some results of actual applications will be presented and it will be shown how this approach generalizes easily to optimal control of the actual processing system. These results generalize those of optimal learning and input conditioning.

Jan 1, 1991

By James S. Browning

In 1975 bituminous coal and lignite production in the United States reached an all-time high of 637 million tons, an increase of 6 percent over production in 1974. The output, valued at $11.9 billion f.o.b. mines, was produced at 5,100 mines in 24 states (6). Coal mining is the largest mining industry in Alabama. Production from Alabama's mines in 1975 was over 21 million tons, and present projections forecast a steady increase in production, with tonnages almost doubling by 1985 (5). Of the total quantity of coal produced, about 16 million tons were consumed in electric power generation and the remainder was used for metallurgical coke production, extraction of chemicals and petroleum based products, and power for industry. The fact that 75 percent of Alabama's power is generated by burning coal attests to the importance of this fossil fuel to the State. Approximately 14 million tons of coal were produced by strip-mining methods in Alabama during 1975 and about 7 million tons were produced by underground mining during the same period. Surface mining is expected to continue at about 14 million tons per year, but by 1980 underground coal mining is expected to increase to about 25 million tons (3). About 7 million tons of surface-mined coal in Alabama is subjected to some means of washing or cleaning. The methods used are screening accompanied by heavy media separation, jigging, tabling and flotation. Some of the simpler approaches employ screening and jigging, or tabling. Except where flotation is used, the screen undersize fraction (finer than 0.25 inch) is rejected, with the result that 10 to 15 percent of the coal is lost. Thus, in the State of Alabama an aggregate of about 1 million tons of coal is wasted annually in the fines which are impounded from treatment of surface-mined coal. The use of the Humphreys spiral to concentrate fine coal was practiced as early as 1947. At that time the Hudson Coal Company (1) used Humphreys spirals to concentrate anthracite fines. In 1950, the use of spirals to treat fine-size

Jan 1, 1977

By Charles A. Beasley

Increased technical and legislative analysis by all parties of interest could result in more efficientand better directed regulatory legislation in the mining industry. Efforts to forestall or frustrate legislation through massive lobbying and public relations efforts are seldom effective over time and often lead to more stringent and far reaching legislation than necessary. The Federal Coal Mine Health and Safety Act of 1969 is perhaps an outstanding example of such insufficiences; a future example may well be regulatory surface mine legislation. Although a lack of extensive hard data seldom enables rapid or sophisticated analysis early in the legislative process, even preliminary analysis may be sufficient. Simple statistical analyses of available data, assessment of the legislative rationale, and subjective appraisal of other non-quantifiable constraints to improved mine safety. An average of 115 underground fatalities at an exposure frequency rate of 0.67 can be reasonably expected in the immediate future, under existing levels of technology, degree of regulation, and economic conditions. If gross unrefined estimates of 6 preparation plant, 5 surface, and 30 strip mining fatalities are assumed, the total fatality industry level could be expected to approximate 156 Serious professional, economic, and technical constraints within the the industry probably preclude any major decrease of these accident levels within the near future

Jan 1, 1972

By J. L. Heaver

All complete plant foods require phosphorus, nitrogen and potassium. And phosphate rock is the primary source for the phosphorus of the inorganic fertilizers. As more and more world food production is grown with these chemical fertilizers and since the Florida field supplies over 30% of the phosphorus component, let us look at the vital phosphate industry. Mining of phosphate rock in Central Florida began in 1891 and production has continued to grow at a steady pace. In 1965 a phosphate mine was opened in Hamilton County, North Florida and one in Beaufort County, North Carolina in 1966 . Since the beginning of mining in 1891, approximately 700 million metric tons of phosphate rock have been produced of this amount one-half was mined in the last 11 years. While the field was not deliberately "high-graded," the best of the known deposits were mined first. Those now being mined, and those yet to be mined, cost more to operate and the product is of lower grade. The U. S. Bureau of Mines' data for 1977 lists "Florida" phosphate rock production as 40.6 million tons; 86% of U. S. production and 85% of "Florida" capacity. The U. S. Bureau of Mines includes North Carolina production in "Florida" statistics so as not to reveal individual data for the one mine operating there. Approximately one-half of "Florida" production is exported, either as rock or as rock equivalent in upgraded products. Deposits of phosphate rock necessary to support present and future production are catalogued as: reserves, paramarginal reserves and resources. Reserves denote deposits which can be mined at a profit now. Paramarginal reserves are defined by the U. S. Bureau of Mines and the U. S. Geological Survey as: that portion of sub-economic resources that a) borders on being capable of production economically, or b) is not commercially available solely because of legal or political circumstances. The " b)" part of this definition may now be expanded to include environmental controls and requirements. Resources are deposits which cannot be mined at a profit at present. Listed in Table I are reasonable values for each of the three categories of phosphate deposits in the northern and southern parts of Central Florida. North Florida and North Carolina.

Jan 1, 1978

By K. T. Brashear

Since the MINER Act of 2006, the minimum static load of in-situ underground mine seals has been increased from 20-psi to either 50-psi if monitoring is conducted or 120-psi if left unmonitored. These minimum strength requirements in seals must be designed, built, and maintained throughout the lifetime of the seal. Due to this, it has become necessary to assess the effectiveness of non-destructive testing (NDT) technologies to determine seal integrity, which in this case, are explored using sonic waves and tracer gases. Through both small and large scale testing, two NDT methods will be evaluated for their abilities to determine integrity of the seal. A sonic wave technique to observe a change in wave velocity to identify faults within the seal material. As a NDT method, tracer gases may be used as a potential indicator of a connection between both sides of the seal material through a series of faults and cracks within the material itself. This paper reviews the history of underground mine seals and discusses the overall assessment of sonic waves and tracer gases to serve as NDT methods for estimating the integrity of these seals.

Feb 23, 2014

By P. Somasundaran

Three major types of solution chemical equilibria involving flotagents (Le. flotation reagents such as collectors, frothers and modifiers), minerals and solution play a crucial role in determining the behavior of complex flotation systems. Minerals of phosphates (apatite and francolite), tungsten (wolframite and scheelite) and associated carbonates (calcite and dolomite) are sparingly soluble in aqueous solution and form dissolved mineral species in bulk solution. Such dissolved species interact with mineral solids, often resulting in surface conversion of the minerals. In addition, they can interact with various flotagents and lead to surface or bulk precipitation and loss of selectivity in the flotation. Relevant solution equilibria of such sparingly soluble minerals and their interactions with oleic acid and structurally modified reagents were determined in this study using a multi-pronged experimental approach. Methods to manipulate and control the solution chemical equilibria and thus achieve selectivity in flotation systems are discussed.

Jan 1, 1990

By J. G. Groppo

A beneficiation process has been developed to provide selective separation of unburned carbon from high loss-of-ignition (LOI)fly ash. Using froth flotation to achieve selective separations requires long residence times and high reagent costs. A proprietary reagent system has been developed to address these limitations. Based on the results obtained from laboratory and pilot-scale investigations, a flowsheet design has been developed to produce two distinct usable products from class F fly ash — low LOI ash and a high-carbon product suit-able for reburning or further upgrading.

Jan 1, 1996

By Kenneth R. Krivanek

In recent years the widespread problems of air and water pollution generated by both population and industrial expansion have become a major public concern. Therefore, many municipalities are striving to achieve more efficient wastewater treatment processes so these wastewater's can be reintroduced into the waterways of our nation with little or no detrimental effects on the future beneficial use of that water. With this, improved treatment comes an ever increasing volume of wastewater sludge which must be disposed of in a manner of minimal impact on the environment. Furthermore, with demand for energy continually accelerating in this nation, our concern over high oil prices and our increasing dependency on foreign oil sources, there has been an ever growing interest in the largest energy source that are nation has, coal. However, surface mining of coal can cause many environmental problems when adequate precautions are not faithfully adhered to. These problems include water pollution from silt and/or clay erosion and acid runoff, produced by oxidation and hydrolysis of pyrite; i.e., FeS2 + 3/02 + H20 + FeSO4 + H2SO4. One method of wastewater sludge disposal which can utilize large volumes of sludge for a beneficial project that may not compound our environmental problems is spray irrigation, to either depleted farmland or to abandoned strip-mined soils. Sludge is characteristically high in organics, as well as having near neutral to alkaline pH properties. With these two qualities it possesses a potential for neutralizing acid strip mine spoils, which would enhance the establishment of a vegetative ground cover. Sludge can accomplish this by lowering the oxidation potential, reducing the solubility of iron and aluminum and by the chelation of metals, thereby

Jan 1, 1977

By Walenty Frydel

The paper deals with highly efficient dust collecting systems of the 10-600 type which constitute new generation installations de- signed to eliminate dust hazard in headings driven with roadheaders. A vortex ventube controlling the air flow in the com- bined ventilation system by means of air vortex generated by the ventube drive unit is also presented. From the results of measurements of under-roof concentrations of methane it appears that the application of the vortex ventube makes it possible to decrease the under-roof accumulation of methane more than 10 times.

Jan 1, 1997

By V. T. McLemore

"Lindgren (1933) defined a belt of alkaline-igneous rocks associated with large quantities of gold and rare earth elements (REE) that extends from Alaska and British Columbia southward into New Mexico, Texas and eastern Mexico. The North American Cordilleran alkaline-igneous belt since has been exploited for numerous types of mineral deposits. In New Mexico, Mid-Tertiary alkaline to calc-alkaline rocks are found with seven types of deposits in these districts: (1) polymetallic epithermal/mesothermal veins, (2) gold-bearing breccias/quartz veins, (3) Cu-Au, Au and Mo porphyry deposits, (4) skarns and carbonate-hosted deposits, (5) iron skarns and replacement bodies (with some gold), (6) gold placers, and (7) Th-REE (with some U, Nb) epithermal veins. Some of New Mexico’s largest gold and REE deposits are found within this belt. Their origin is not well understood, but a compilation of new data (age dates, isotopic and chemical analyses) allows for a better understanding. The diversity of igneous rocks and associated mineral deposits along this belt suggests that this region is characterized by highly fractionated and differentiated; multiple pulses of magmas and involves both upper mantle and lower crustal sources. Once magmas and metal-rich fluids reached shallow levels, local structures and wall rock compositions determined distribution of and final style of intrusions and resulting mineral deposits. INTRODUCTION Lindgren (1933) was one of the first geologists who noted that a belt of alkaline-igneous rocks extends from Alaska and British Columbia southward into New Mexico, Trans-Pecos Texas, and eastern Mexico (Fig. 1) and that these rocks contain relatively large quantities of gold, fluorine, zirconium, rare earth elements (REE), and other elements. Since then, the North American Cordilleran alkaline-igneous belt has been explored and exploited for numerous types of mineral deposits, especially gold. The North American Cordilleran alkaline belt is a north-south belt of alkaline igneous rocks and crustal thickening, roughly coinciding with the Great Plains physiographic margin with the Basin and Range (Rio Grande rift) and Rocky Mountains physiographic provinces (Mutschler et al., 1985, 1991; Bonham, 1988; Thompson, 1991a; Richards, 1995; McLemore, 1996; Jensen and Barton, 2000; Kelley and Luddington, 2002). Deposits within this belt have produced significant amounts of gold in the United States and Canada and include Cripple Creek, Colorado (702 metric tons of gold production), Black Hills, South Dakota (235 metric tons gold production) and Landsky-Zortman, Montana. In New Mexico, the North American Cordilleran alkaline belt extends from the Sangre de Cristo Mountains near Raton, southward to the Cornudas Mountains, in the northern Trans-Pecos alkaline belt (Fig. 2). The alkaline-igneous related mineral deposits in New Mexico have been referred to as Great Plains Margin (GPM) deposits by North and McLemore (1986, 1988) and McLemore (1996, 2001). Alternative classifications by other workers include Au-Ag-Te veins (Cox and Bagby, 1986; Bliss et al., 1992; Kelley et al., 1998), alkalic-gold or alkaline-igneous related gold deposits (Fulp and Woodward, 1991a; Thompson, 1991a, b; Bonham, 1988; Mutschler et al., 1985, 1991; Richards, 1995), porphyry gold deposits, and the North American Cordilleran belt of alkaline igneous rocks (Woolley, 1987; Mutschler et al., 1991)."

Jan 1, 2015

By Y. J. Wang

Stall or aerodynamic stall of axial-flow fans has long been recognized as an important operational problem in mine ventilation. To develop a technique for characterizing fan stall in multiple-fan ventilation networks, a research project was initiated through the Generic Mineral Technology Center for Mine Systems Design and Ground Control. Considering that fan stall is related to multiple operating points, this paper discusses a numerical model for multiple-fan ventilation networks, design of the experimental setup for two-and three-fan ventilation networks, and numerical methods for solving multiple networks solutions. It is hoped that the results of this project will lead to an innovative method of ventilation network analysis and simulation, thus preventing stall.

Jan 1, 1991

By B. Bag

Saturated and unsaturated fatty acids are used in the flotation of iron values present in iron ore. Among the several fatty acids, oleic acid and its sodium salt are widely used. To substantiate the flotation results, the quantum chemical calculations of a few such acids have been carried out by adopting the semi-empirical AM1 method. These acids have been further optimized in the presence of an iron atom. The electronic interaction of the polar carboxylic head group of oleic acid with the iron atom is higher compared to the other acids. The numerical results support the flotation behavior of iron ore with oleic acid. Key words: Iron ore, Flotation, Fatty acids, Quantum chemical calculations, Semi-empirical AM1 method

Jan 1, 2009

By A. L. Coello Velázquez

The subject of this paper is particle population balance models (PBM) that describe mineral impact crushing behavior; it is mainly concerned with the selection and fragmentation distribution function due to their importance in this context. The data obtained by Datta (1999) by applying impact pendulum testing to single limestone particles, used by Austin (2002, 2004a and 2004b) to obtain the principal parity of fragmentation functions, were processed in order to compare them with the results of other authors, such as Nikolov (2002 and 2004) and Vogel and Peukert (2003 and 2005) so as to increase knowledge of impact crushing. From this data it has been possible to obtain the performance models of the principal parameters of fragmentation function, thereby reducing the number of experiments necessary to model the impact crushing process. The authors also propose a simplification of the selection function model posited by Austin (2002).

Jan 1, 2011

By Warren E. Morrison

The expansion of the United States economy in the postwar period has had a tremendous impact on the demand for energy. Not only has total energy consumption increased at an unprecedented rate, but there have been major shifts in the composition or mix of energy resources within the end-use sectors. Because of the numerous interrelationships between substitutable energy resources and their markets, the energy economy can only be analyzed in terms of the trends of its component parts. This problem takes on additional complexity when attempting to chart the nation's future energy requirements. Total energy consumption can be forecast with reasonable accuracy for periods up to 15 years by relating this to projections of economic indicators. However, forecasting the component parts of the energy economy constitutes a dilemma in that the sum of the projected parts frequently exceeds predictions for total energy. Areas of uncertainty in energy forecasting tend to mount rapidly when proceeding from total energy to the consideration of specific energy resources consumed as fuel, power, or raw materials.

Jan 1, 1965

By J. A. Meech

An analysis of screen design options on the operating efficiency of secondary crushing plants has been conducted using a dynamic computer model. The model allows for the simulation of a wide variety of crushing circuits and can be run on either a microcomputer (IBM PC/XT) or a large time-sharing mainframe computer. Size reduction and separation characteristics of crushers and screens are based on standard manufacturer design and performance data. Input/output routines are available in tabular, alarm or strip chart recorder modes to facilitate operation of the program. A number of alternate circuit designs are compared to show the influence of surge capacity, screen size and area, screen deck location, and closed side crusher settings on the operation of a 10,000 ton per day plant. The program is currently in use at Queen's University to teach plant operations and control. It has potential to be a valuable tool for operator training.

Jan 1, 1985

By R. L. Grayson

A goal programming-based worker scheduling model has been incorporated in the Mine Management Support System (MMSS) for assigning workers to prioritized jobs on a shift basis. In the model the accomplishment of each regular and non-regular job is a goal. The objective is minimization of the deviations away from the goals. A number of coefficients are used as premultipliers of the decision variables in order to address practical considerations associated with the utilization of workers and the requirements of jobs. Some of these premultipliers will be updated expertly within MMSS, timely updating the statuses of the dynamic parameters.

Jan 1, 1991

By J. H. Hammarstrom, S. M. Fortier, W. C. Day, S. J. Ryker, R. R. Seal

"The United States’ supply of critical minerals has been a concern and a source of potential strategic vulnerabilities for U.S. economic and national security interests for decades (for example, see Strategic and Critical Minerals Stockpiling Act, 1939). More recently, with the rapid increase in the types of materials being used in advanced technologies (Fortier et al. 2018a), and geopolitical events surrounding the supply of rare earth elements (Ting and Seaman, 2013), among other developments, the critical minerals issue has again achieved a high level of visibility within the U.S. government (Executive Order 13817 (2017)).In this paper, the U.S. Geological Survey (USGS) provides an overview of its ongoing focus on critical minerals through the agency’s core competencies in mineral information, mineral resource assessments, geologic and topographic mapping, geophysical surveys and mineral resource research. Aspects of the multifaceted critical minerals issue addressed here include:• Identifying minerals that meet the definition of “critical” provided in Executive Order 13817.• U.S. net import reliance for critical mineral raw materials.• Current status of domestic critical mineral resource assessments.• Current status of topographic and geologic mapping, and geophysical survey coverage of the United States.• The Earth Mapping Resources Initiative (Earth MRI) to support future critical mineral exploration.• Critical mineral potential of waste streams from extractive industries.Identifying minerals as criticalU.S. government agencies and other organizations use a number of existing definitions and criteria to identify a mineral or mineral material as critical, strategic or otherwise important. The executive order defined a “critical mineral” to be “(i) a nonfuel mineral or mineral material essential to the economic and national security of the United States, (ii) the supply chain of which is vulnerable to disruption, and (iii) that serves an essential function in the manufacturing of a product, the absence of which would have significant consequences for our economy and national security.” This definition is broadly consistent with that defined by the National Research Council (NRC, 2008) and may be summarized as “essential in use” and “subject to disruption of supply.” Virtually all of the dozens of critical minerals studies conducted since the 2008 NRC report have used some variation of this same definition (Hayes and McCullough, 2018)."

May 1, 2019