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By J. H. Howard

The purposes of this report are to summarize the findings of the Committee on the Challenges of Modern Society Non-electrical Project (a working committee of the North Atlantic Treaty Organization) and also, thereby, to provide an introduction and review of the current situation regarding non-electrical applications to those who are interested in the subject.

Jan 1, 1975

By Myles E. Robinson

Significant changes in the markets for coal have taken place since World War II, As used in this study the term ?coal? will refer to bituminous coal, The anthracite industry in size, characteristics, and problems differs materially from the bituminous coal industry, These changes have both influenced and been influenced by the mechanization of mines, and by decreased distribution costs, especially in transportation. It is the purpose of this paper to examine these post-war changes, to assess their impact upon the production and distribution of coal, and to explore future market developments in the light of past and present trends and relationships. The layman lacks adequate informatian on the production, demand, and distribution of coal. There are two reasons for this. First, there is a relative lack of statistics coveting the industry, Coal operators and distributors are not required to file with any government agency the type of much more complete statistics filed by the railroads and public utilities with national and State agencies. The Bureau of Mines assembles much useful information on the coal industry, but several areas, including that of investment and finance, have no central depository which can be used to keep the public informed of the nature and extent of the industry and its problems.

Jan 1, 1964

By Lee S. Richardson

Silicon is usually considered to be a useful metallic alloying element. To be more truthful, it is not a metal at all, but a semiconductor, whose electrical resistance (when pure) is high and decreases with temperature. We will join the metallurgists, at least for this paper, and refer to it as a metal. In its commercially available form, silicon is metallic in appearance, brittle, with a density of 2.33, less than that of aluminum. Silicon dioxide or quartz has a high heat of formation, which not only makes the metal a useful reductant for other materials, but also makes it difficult to reduce from its ore. The melting point is 1412°C, slightly less than steel, but substantially higher than aluminum or cast iron. The alloys of silicon with iron, usually called ferrosilicons, have some unique advantages. The melting points of most alloys are substantially below those of iron or silicon (Fig. 1). The two major compounds formed (FeSi and FeSi2) help somewhat in the reduction of silicon by their energies of formation, but the influence of these phases on the mechanical properties is more important. Four major groups of alloys are made -- silicon metal (>95% silicon), 75-85% ferrosilicon, 50% ferrosilicon, and silvery pig iron (12-22% silicon). The alloys between 50 and 65% silicon and between 25 and 40% silicon are normally avoided because of structural instabilities, presumably of the two compounds, leading to disintegration of the alloys on cooling.

Jan 1, 1974

By S. C. Gaillard

Tailings are made of ground rock that is left over from removing valuable minerals. The tailings are usually fine particles that cause environmental issues for storage and disposal. Disposal of tailings is a growing concern, as more tailings are produced from the increasing demand for mined material (ITRC, 2008). This project proposes a way to convert the mine waste to a useful product. Tailings were selected from a South Carolina crushed stone quarry, the products of which are used for road beds, sidewalks, asphalt and driveways. These tailings were processed to generate synthetic aggregates for construction applications. The synthetic aggregate creates a product that could be used for many purposes, including aggregate for sidewalks, driveways, roads and building materials. Testing methods followed the North Carolina Department of Transportation (NCDOT) guidelines for physical testing of coarse natural aggregate, which are sieve analysis, Los Angeles abrasion, absorption, specific gravity and soundness test. The synthetic aggregate produced passed all tests for NCDOT and, in some instances, rated better than a natural aggregate. Using the tailings from the crushed stone and mining industry would convert the waste into a valuable, marketable product.

Jan 1, 2013

By A. R. Laplante

A novel methodology to estimate gold recovery by gravity is presented. The methodology makes use of a population balance model which represents gold liberation, breakage and classification behaviour and applies pre-concentration and recovery performance curves to gravity-recoverable gold to predict overall recovery. Derivation of the necessary parameters is explained and demonstrated using data from an actual gravity circuit and one projected application. The methodology makes it possible to estimate the performance of circuits with large gold circulating loads and relatively low unit recoveries (e.g. jigs), or with high recoveries on a bleed of the circulating load (e.g. Knelson concentrators).

Jan 1, 1994

By W. A. Crosby

The ability of open pit mines to steepen overall final wall angles allows significant cost reductions as a result of reduced waste movement requirements. Final wall angles are principally controlled by three factors: geological conditions; hydrological conditions; and wall control blasting practices. The first of these factors is not controllable by the mine operator, the second can be influenced to some degree, but the last one certainly can be controlled, hence the current interest in final wall blasting practice at many mining companies. This paper discusses common blasting techniques employed to steepen final pit walls and outlines the attractiveness of moving from small hole high cost systems to the use of full size production drills as a means of reducing wall control blast costs. Attempts to make this change have been limited at many mines by the physical size of the drills and their inability to reverse drill. In the past, pres pi it, pre-shear or trim holes have had to be drilled vertically, at considerable distance from the upper bench toe, with the result that inter-berm face stability is reduced and final wall angles have to be made somewhat more shallow than desirable. The paper concludes with a description of how these problems can be overcome by utilizing the new Bucyrus 39R which has the capability of drilling at a ?15 degree angle underneath the machine. It is concluded that the resulting wall control blast designs will offer large mines improved final wall angles with resulting significant overall cost reductions.

Jan 1, 1998

By Joseph F. Shirley

A froth flotation plant to recover by-product molybdenite must be designed specifically for the selected separation process and the type of ore being treated. However, some general rules concerning by-product molybdenite plant design can be suggested that would be valid for most processes. The term by-product molybdenite in this paper is limited to the recovery of molybdenite from copper porphyry ores, which essentially amounts to selectively separating molybdenite from copper and iron sulfide concentrates. In addition, most of the discussions would apply only to the almost universally used approach of floating the molybdenite and depressing the copper and iron sulfide minerals.

Jan 1, 1979

By C. G. Anderson

The treatment of materials for the recovery of the precious metals imposes many processing and environmental challenges. Sunshine Mining and Refining Company has developed hydrometallurgical technology for recovery of values from refractory precious metal materials. At Sunshine, the industrial focus of these processes has been for the direct recovery of silver without cyanidation. However, recent work has indicated that these technologies can provide a means for treating complex, refractory gold concentrates. This will be the focus of this paper. The practice of pretreating ores and concentrates to make them more amenable to cyanidation is becoming more common. Several pretreatment options for sulfide concentrates containing gold include roasting, bio-leaching, direct pressure oxidation and nitrogen species catalyzed pressure oxidation. The industrial use of nitrogen species catalyzed pressure oxidation has been limited to the Sunshine refinery where its focus has been for the treatment of silver concentrates. Much of the reluctance, outside of Sunshine, to use this type of technology may be based on the perception that high costs are associated with using nitrogen species (e.g. nitric acid, sodium nitrite) to leach. Also, the use of nitrogen species catalyzed pressure oxidation on an industrial scale is unfamiliar to most metallurgical professionals. A summary of pressure leaching processes which utilize nitrogen species as a catalyst is presented in Tables 1 and 2.

Jan 1, 1996

By A. Cecala, J. Noll, J. Hummer

The National Institute for Occupational Safety and Health has observed that many control rooms and operator compartments in the U.S. mining industry do not have filtration systems capable of maintaining low dust concentrations in these areas. In this study at a mineral processing plant, to reduce respirable dust concentrations in a control room that had no cleaning system for intake air, a filtration and pressurization system originally designed for enclosed cabs was modified and installed. This system was composed of two filtering units: one to filter outside air and one to filter and recirculate the air inside the control room. Eighty-seven percent of submicrometer particles were reduced by the system under static conditions. This means that greater than 87 percent of respirable dust particles should be reduced as the particle-size distribution of respirable dust particles is greater than that of submicrometer particles, and filtration systems usually are more efficient in capturing the larger particles. A positive pressure near 0.02 inches of water gauge was produced, which is an important component of an effective system and minimizes the entry of particles, such as dust, into the room. The intake airflow was around 118 cfm, greater than the airflow suggested by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) for acceptable indoor air quality. After one year, the loading of the filter caused the airflow to decrease to 80 cfm, which still produces acceptable indoor air quality. Due to the loading of the filters, the reduction efficiency for submicrometer particles under static conditions increased to 94 percent from 87 percent.

Jan 1, 2015

By A. D. Randolph

Comminution represents one of the major costs of mineral recovery from low-grade ores. Efficient mineral recovery in a typical low-grade ore grinding-flo¬tation process depends on grinding the ore small enough to liberate mineralization without producing excessive slimes, which would result in higher power and flotation reagent costs. Size criteria for efficient grinding should be stated in terms of the distribution of mineralization sizes, but as the mineralization-size distribution is difficult to determine, less desirable criteria of absolute particle-size distribution (PSD) are used in practice. Thus, there is considerable incentive to be able to analyze and predict the PSD performance of grinding circuits for control and optimization of the process. Any realistic model of a grinding circuit must account for recycle of oversize material; such oversize recycle adds to the total mill load and limits total production rate. Simulation of such closed-circuit operation to study grind factors affecting total throughput can be done in a straightforward fashion provided recycle calculations can be added to an accurate input-output model of PSD in the grinding mill itself. Such a total simulation of mill performance is of obvious practical value in assessing the practicality and benefits of various over-all mill control schemes and/or modes of operation. For example, considerable interest has been shown in the development of continuous on-line particle-size sensors and such instruments should be an operating reality in a few years. A total closed-circuit PSD model of this type would be invaluable in the utilization of, and in predicting the pay-out from, such an on-line particle-size sensor. The purpose of this paper is to present a new approach to the development of an input-output PSD model of a grinding mill. The model is continuous in the par¬ticle size coordinate, L, and is based on the principle of a particle population balance along the particle size coordinate. Most previous studies of the grinding unit operation attempt to relate power

Jan 1, 1971

By Kenneth P. Neumann

The development of the Cyprus Thompson Creek Molybdenum Deposit near Challis, Idaho, began in 1967 when the first mining claims were staked on the intrusive rock outcrop. Exploration drilling continued for the next 14 years. During 1978, a decision was made to develop the deposit. In December, 1980, approval of the Environmental Impact Statement was received and construction of facilities and waste rock removal began. By the middle of 1983, 126 M metric tons of rock had been removed and all facilities were completed. The high work ethic of Cyprus Thompson Creek employees combined with innovation has made the mine one of the most efficient in the United States today.

Jan 1, 1983

By J. R. Schafler, J. L. Brinkman

"The US coal mining industry has suffered a recent decline in profits caused by a combination of decline in commodity demand and more restrictive government regulation, forcing coal mining companies to cease production in numerous mines. A 40% decrease in the total number of coal mines occurred from 1994 to 2000. The number of mines remained relatively constant until 2008 when a change of government sparked a series of new environmental regulations which have contributed to another 15% decrease from 2008 to 2016. In contrast, production has only decreased by 3%, increasing from 1994 to 2008, and then decreasing since 2008. However, this value is skewed by large increases in sub-bituminous coal production and decreases in other coal ranks. Several aspects assist in executive decisions on mine longevity and economic worth. Studies of open source mine data collected by mandated government surveys coupled with commodity history can be used to find relationships between mine closures and these elements, which include statistics on production tonnage, seam height, coal rank, etc. This paper looks at coal mining trends since 1994 by comparing mine, market, and regulation factors that may influence mine closure. INTRODUCTION The US coal mining industry is currently experiencing a decline in both demand and commodity price while facing implementation of more stringent air and water pollution regulations. Company profits have decreased significantly, forcing several major companies to declare bankruptcy. The industry was required to adapt to survive. Many of these companies have adjusted by abandoning mines; the last two decades have seen a drastic decrease in the number of mines. To discover the primary causes of this downturn, three major aspects must be studied: properties of abandoned mines, commodity history, and regulatory impact. TRENDS SINCE 1994 Each year, US coal mines are required to submit data on a wide variety of categories to the Mine Safety and Health Administration (MSHA) and the US Energy Information Administration (EIA). This data includes administrative records, production values, and information regarding the attributes of the mined material and the mine itself. Each year since 1996, EIA has released a report summarizing the data from two years prior. Additionally, MSHA maintains a database containing a collection of all the most current data. These resources are the primary sources for the following figures."

Jan 1, 2017

By Mark E. Emerson

Foreign and domestic companies find the mineral potential of this country's stern public lands, its capital markets, political stability, and "open-door" policy attractive for hard mineral exploration. Traditionally, exploration in the US has been geographically based and responsibility oriented at the district level. The 1970s brought a decentralized approach to exploration as major non-metal companies began to diversify into hard minerals. The emphasis was on capital intensive metal and energy projects involving bulk-tonnages. The recent economic downturn in metals has caused many of the new participants to withdraw from the mineral scene. The surviving companies have shifted their emphasis toward medium scale precious metal projects having high operating margins and rapid return on equity. Exploration expenditures in the United States are now principally focused on gold and silver to the exclusion of practically all other commodities. In the search for precious metals companies have scaled back their exploration efforts and have began to apply new approaches to target selection. The search is being assisted by rapidly evolving conceptual models. The change in orientation has led to numerous new discoveries. The finds are essentially "rediscoveries" that c,-re previously uneconomic. The majority are low-grade surface deposits that have involved low discovery costs and short lead times for development by low-cost mining and beneficiation methods. The emphasis on gold to the exclusion of all other commodities raises questions regarding the direction of exploration in the US for the rest of the 80s.

Jan 1, 1984

By J. B. Griffiths

Clearly there is a tremendous need for assistance in Eastern Europe since most industries must undergo major restructuring. The new governments face many dilemmas, the first task being to establish an order of priorities to deal with the numerous problems at hand. Issues such as the standard of living take low priority compared with market economy and ecological problems. The concept of a Comecon market is now virtually non-existent and trade in roubles ceased from 1991. From this time onwards countries were obliged to trade using free market prices. Governments must also avoid the economic mistakes of countries such as Poland with its high devaluation and lack of economic control and, if possible, contain inflation and unemployment. The privatization of Eastern European enterprises raises considerable difficulties, particularly for large corporations, employing anywhere from 50-100,000 people, which played a major role in the national economy. Whichever method is selected, however, still has to overcome the problem of lack of capital and evaluating the national property. For example, earnings represent only a small percentage of the value of these national industries and thus cannot convert to private ownership without foreign capital investment, either direct or as joint venture capital.

Jan 1, 1992

By Roger C. Wilmoth

The most common method of treating mine drainage to prevent water pollution consists of neutralization and aeration. This process removes the acidity, iron, aluminum, and some other heavy metals, but does not render a water suitable for domestic or industrial use because of the high dissolved solids, hardness, and sulfate in the treated water. The Environmental Protection Agency (EPA), has been sponsoring and conducting research since 1966 on the use of reverse osmosis (R.O.) for the treatment of mine drainage. This process has been found to be highly effective in the removal of nearly all the dissolved solids. In addition, since R.O. is a concentrating process, potentials for recovery of valuable heavy metals are possible. This paper is a review of the state-of-the-art on the treatment of mine drainage by reverse osmosis.

Jan 1, 1972

By Y. Guan

The dissolution behavior of copper and gold from their pure state and from Au/Cu alloys in cyanide solutions has been investigated using a rotating disc. Oxygen was used as an oxidant. The effect of the composition of the alloys, stirring speed of the disc, concentration of lixiviants and temperature on the overall dissolution kinetics has been studied. Gold/copper alloys of three compositions were used in this study. The atomic percent of gold in these alloys was 75, 50 and 25, respectively. The dissolution behavior of these three alloys was compared with that of pure gold and of copper under the same chemical conditions. In general, the dissolution of copper and gold from alloys is partially controlled by surface chemical reaction and largely by mass transfer.

Jan 1, 1992

By J. Herbst, J. Groppo, A. Noble, R. Q. Honaker

"Coal and coal byproducts produced annually contain enough rare earth elements (REEs) to meet current U.S. demand. The REEs exist in the form of minerals, ion-exchanged elements associated with clays and chemically bonded elements within the organic coal matrix. Researchers at three universities have collaborated to evaluate the effectiveness of existing physical and chemical concentration processes for the recovery of the REEs. The efforts have found that physical separation processes can increase the total REE content in the thickener underflow material collected from a Central Appalachian coal cleaning facility from around 300 ppm to values greater than 17,500 ppm on an ash basis. On the other hand, leaching was effective in recovering REEs from coarse middlings materials collected from multiple coal basins as indicated by recovery values exceeding 80%. Based on material characterization data and process evaluations conducted for several potential feed coal sources, economic recovery of the REEs will require byproduct production of both clean coal and REE concentrate using a process flowsheet that is unique for each source. INTRODUCTION Recent studies initiated by NETL showed that U.S. coals contain significant amounts of rare earth elements (REEs), suggesting that rare earth minerals (REMs) and/or REEs can be produced as byproducts [1]. According to the report, the richest source of REEs is the Central Appalachian coal. At present, there are 208 coal preparation plants located in the region (WV, KY, PA, VA, AL, TN) with a capacity of 166,495 tons/hr or more than 1 billion tons annually [2]. If only a portion of these plants are retrofitted with advanced separation processes, the U.S. coal industry can become a significant producer of RE minerals as byproducts. An inherent advantage of becoming a byproduct producer of REEs is that no mining cost needs to be part of the product cost. Other researchers have also shown that coal can be a significant source of REEs. The average sum of the rare earth plus yttrium (REY) concentration of the world coal is approximately 68.5 ppm, which is lower than the corresponding upper crustal concentration (UCC) (168.4 ppm). However, the average REY content of the mineral matter in the world (404 ppm) and U.S. coals (517 ppm) are 3 times higher than the average UCC. Some of the mineral matter in Russian and Chinese coals have REY concentrations in the range of 0.68 to 2.03% and contain a better source of higher value REYs than many primary rare earth deposits [3]."

Jan 1, 2017

By C. L. McKenzie

American Girl Mine is located in the Cargo Muchacho Mountains in the southeastern Imperial Valley of Southern California. Production from the current open pit mine and heap leach recovery system began in early 1989. Previous mining and gold recovery took place commencing in 1987 at the Padre Madre site, situated adjacent to the American Girl site to the southwest. In mid-1990, a 790-tonne-per-day underground gold mine and mill went into production. Approximately 6,500 troy ounces of gold per month are recovered from the combined open pit underground mine operation. Copper in the form of Azurite [Cu3(CO3)2(OH)2] and Malachite [Cu2CO3(OH)2] are abundant in the mined ores (Henshaw, 1942). The high solubility of these minerals in caustic cyanide solutions has a negative impact on carbon adsorption and electrowin processes. This paper presents the results of monitoring programs, process chemistry, and control changes introduced at American Girl Mine to abate production complications in the refinery and measures taken to minimize solution gold losses in the adsorption circuit(s).

Jan 1, 1993

By Edmond F. Lawrence

The Calico area lies within the Walker Lane fault zone, six miles north of Schurz, Nevada. The mineralized area is overlain by a thick section of Tertiary tuffs and ash-flows, that have been intruded by a series of andesite plug, dikes, and sills. The pre-Tertiary rocks outcrops only in two areas at one to two miles distance from the drilling areas. Underlying the volcanics are sediments ranging from siltstones, sandstone, calcareous shales, to carbonates of the Luning sequence. These have been intruded by one or more phaneritic intrusives ranging in composition from quartz diorite to quartz monzonite, with the development of a skarn zone on the south flank that contains extensive mineralization consisting of magnetite, pyrrhotite, pyrite, and chalcopytite, with traces of sphalerite, galena, and molybdenite. The magnetite, pyrrhotite, and part of the pyrite appears to be contemporaneous with the skarn, while, part of the chalcopyrite, galena, sphalerite, molybdenite, quartz, and calcite, occurs as minute veinlets cutting the other minerals. This later mineralization may be associated with a late stage of the same sequence, or possibly associated with another intrusive to the southwest. Geophysical work has consisted of aerial magnetics, ground magnetics, gravity, seismic, and induced polarization surveys. Preliminary induced polarization surveys indicated anomalies at depth, both over the magnetic anomaly and to the northwest. Subsequent IP work confirmed this earlier anomaly, and drilling disclosed extensive mineralization at depths of 400 feet on the northwest end and over 1,000 feet to the southeast.

Jan 1, 1967

By George J. Conroy

Results of a long-term program of electrical parameter measurement in under-ground coal mine working sections, performed by The Pennsylvania State University under U. S. Bureau of Mines sponsorship, are utilized as the basis for an analysis of the electrical energy requirements during operation. A model section is hypothesized, developed from the average or most representative characteristics as determined from tabulations of the measurements. Performance factors of the model section's machine complement are then analyzed, particularly with regard to the energy required per ton of raw coal cut and delivered from the section. Results are given in kilowatt-hours per ton.

Jan 1, 1977