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economic small kaolin magnetic separator in leon

economic small kaolin magnetic separator in leon

This chapter provides background information on the exploration, mining, and processing of mineral commodities. This is followed by a brief overview of the current state of technology in these fields. The role of research and development in improving technology, and thus in offsetting the adverse effects of mineral-resource depletion over time, are highlighted

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2 overview of technology and mining | evolutionary and

Mining is first and foremost a source of mineral commodities that all countries find essential for maintaining and improving their standards of living. Mined materials are needed to construct roads and hospitals, to build automobiles and houses, to make computers and satellites, to generate electricity, and to provide the many other goods and services that consumers enjoy

In addition, mining is economically important to producing regions and countries. It provides employment, dividends, and taxes that pay for hospitals, schools, and public facilities. The mining industry produces a trained workforce and small businesses that can service communities and may initiate related businesses. Mining also yields foreign exchange and accounts for a significant portion of gross domestic product. Mining fosters a number of associated activities, such as manufacturing of mining equipment, provision of engineering and environmental services, and the development of world-class universities in the fields of geology, mining engineering, and metallurgy. The economic opportunities and wealth generated by mining for many producing countries are substantial

Mining is particularly important to the U.S. economy because the United States is one of the world’s largest consumers of mineral products and one of the world’s largest producers. In fact, the United States is the world’s largest single consumer of many mineral commodities

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The United States satisfies some of its huge demand for mineral commodities by imports (Figure 2-1). For decades, the country has imported alumina and aluminum, iron ore and steel, manganese, tin, copper, and other mineral commodities. Nevertheless, the country is also a major producing country and a net exporter of a several mineral commodities, most notably gold. As Table 2-1 shows, the United States produces huge quantities of coal, iron ore, copper, phosphate rock, and zinc, as well as many other mineral commodities that are either exported directly or used in products that can be exported

According to the U.S. Geological Survey (USGS), the value of the nonfuel1 mineral commodities produced in the United States by mining totaled some $39 billion in 1999 (USGS, 2000). The value of processed materials of mineral origin produced in the United States in 1999 was estimated to be $422 billion (USGS, 2000). U.S. production of coal in 1999 was 1,094 million short tons, which represents an estimated value of $27 billion (EIA, 1999a). However, the true contribution of mining to the U.S. economy is not fully reflected in these figures. For example, the economic impact of energy from coal, which produces 22 percent of the nation’s energy and about 56 percent of its electricity, is not included

The Bureau of Labor Statistics in the U.S. Department of Commence estimates that the number of people directly employed in metal mining is about 45,000, in coal about 80,000, and in industrial minerals about 114,000 (U.S. Department of Labor, 2000a). Together these figures account for less than 1 percent of the country’s total employment in the goods-producing sector (U.S. Department of Labor, 2000a). The low employment number reflects the great advances in technology and productivity in all mining sectors and lower production costs

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In states and regions where mining is concentrated the industry plays a much more important role in the local economy. Overall, the economy cannot function without minerals and the products made from them. Mining in the United States produces metals, industrial minerals, coal, and uranium. All 50 states mine either sand and gravel or crushed stone for construction aggregate, and the mining of other commodities is widespread. The contribution of mining extends to jobs and related benefits to downstream products such as automobiles, railroads, buildings, and other community facilities

Metal mining, which was once widespread, is now largely concentrated in the West (Figures 2-2a and 2-2b), although it is still important in Michigan, Minnesota, Missouri, New York, and Tennessee. The minerals mined include iron, copper, gold, silver, molybdenum, zinc, and a number of valuable but less common metals. Most are sold as commodities at prices set by exchanges rather than by producers. Moreover, the high value-to-weight ratio of most metals means they can be sold in global markets, forcing domestic producers to compete with foreign operations

The trend in metal mining has been toward fewer, larger, more efficient facilities. Through mergers and acquisitions, the number of companies has decreased, and foreign ownership has increased. The search for economies of scale has also intensified. Mines now employ fewer people per unit of output, and operators are eager to adopt new technologies to increase their efficiency, which benefits customers and reduces the cost of products. Because metal mines have no control over commodity prices, their prevailing philosophy to survive is that they must cut costs. As a result, most domestic metal mining companies have largely done away with in-house research and development, and many are reluctant to invest in technology development for which there is no immediate need

2 overview of technology and mining | evolutionary and

Industrial minerals, which are critical raw materials for the construction industry, agriculture, and the chemical and manufacturing sectors of the economy, are produced by more than 6,400 companies from some 11,000 mines, quarries, and plants widely scattered throughout the country (Figure 2-3a and 2-3b). Most industrial minerals have a degree of price flexibility because international competition in the domestic market is limited. Although some companies and plants are large, size is not always necessary for economic success. However, obtaining permits for new mines and quarries is often difficult, especially near urban areas, and this may favor larger operations and more underground mining in the future

The major industrial materials are crushed stone, sand, and gravel, which are lumped together as “aggregate” and comprise about 75 percent of the total value of all industrial minerals. A wide variety of other materials are also mined, such as limestone, building stone, specialty sand, clay, and gypsum for construction; phosphate rock, potash, and sulfur for agriculture2; and salt, lime, soda ash, borates, magnesium compounds, sodium sulfate, rare earths, bromine, and iodine for the chemical industries. Industrial materials also include a myriad of substances used in pigments, coatings, fillers and extenders, filtering aids, ceramics, glass, refractory raw materials, and other products

Certain industrial minerals, such as aggregates and limestone, are sometimes said to have “place value.” That is, they are low-value, bulk commodities used in such large quantities that nearby sources are almost mandatory. Competition from imports is generally unlikely, although exceptions can be found. Low production costs combined with low ocean transportation costs, allows cement clinker to be imported from Canada, Taiwan, Scandinavia, and China. At one end of the spectrum, some materials, such as domestic high-grade kaolin, require extensive processing and are so valuable that the United States is a major exporter. At the other end, materials such as natural graphite and sheet mica are so rare and domestic sources so poor that the United States imports 100 percent of its needs

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Unlike the aggregate industry, which is spread over most of the country, some industrial minerals are concentrated in certain parts of the country (Figures 2-3a and 2-3b). Phosphate mining is confined to Florida, North Carolina, Idaho, Utah, and Wyoming. Newly mined sulfur comes from the offshore Gulf of Mexico and western Texas, but recovered sulfur comes from many sources, such as power plants, smelters, and petroleum refineries. The Carolinas and Georgia are the only sources of high-grade kaolin and certain refractory raw materials. The United States has had only one significant rare-earth mine, located in the desert in southeastern California. Potash, once mined in New Mexico and Utah, now comes mostly from western Canada, where production costs are lower

The technologies used in the industrial-minerals sector vary widely, from relatively simple mining, crushing, and sizing technologies for common aggregates to highly sophisticated technologies for higher value minerals, such as kaolin and certain refractory raw materials. Agricultural minerals, including phosphates, potash, and sulfur, are in a technological middle range. Uranium can be recovered from phosphate processing. Some investments in new technologies for industrial minerals are intended to increase productivity, but most are intended to produce higher quality products to meet market demands

Coal is the most important fuel mineral mined in the United States. With annual production in excess of a billion tons since 1994, the United States is the second largest producer of coal in the world. Nearly 90 percent of this production is used for electricity generation; coal accounts for about 56 percent of the electricity generated in the United States (EIA, 1999b). In recent years coal has provided about 22 percent of all of the energy consumed in the United States. Although the nation’s reserves of coal are very large, increases in production have been rather small

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Several projections show that coal will lose market share to natural gas, a trend that could be accelerated by concerns over global warming (Abelson, 2000). Coal production may benefit in the short run, however, from electricity deregulation as coal-fired plants use more of their increased generating capacity. With the price of natural gas increasing by more than 100 percent in recent months, projections of future energy mix must be viewed with caution, at least in the short term

Coal is found in many areas of the United States (Figure 2-4), although there are regional differences in the quantity and quality. Anthracite is found primarily in northeastern Pennsylvania; bituminous coking coals are found throughout the Appalachian region; and other bituminous grades and subbituminous coals are widely distributed throughout Appalachia, the Midwest, and western states

Deposits of lignite of economic value are found in Montana and the Dakotas, as well as in Texas and Mississippi. Because lignite is about 40 percent water, it is ordinarily used in power plants near the deposits. In recent years considerable research has been focused on making synthetic liquid fuels from lignite

2 overview of technology and mining | evolutionary and

Some Appalachian and most midcontinent coals have high sulfur contents and thus generate sulfur dioxide when burned in a power plant. Under current environmental regulations effluent gases may have to be scrubbed and the sulfur sequestered. Many power producers have found it more economical to purchase coals from western states. These coals have less sulfur and are preferrable even though they have lower calorific power (energy content). Therefore, the market share of large western mines is increasing. Most western coals are mined from large surface mines, and delivery costs are low because of the availability of rail transportation. Because the capital costs of sulfur scrubbing are high, low-sulfur coal from Montana, Wyoming, and Colorado can be shipped economically by rail over long distances. Concerns about mercury emissions from coal-fired power plants may also influence the future use of coal

The extensive coal reserves in Utah, Arizona, Colorado, and New Mexico are large enough to produce power to meet local needs, as well as for “wheeling” (transporting energy) over high-voltage transmission lines to Pacific coast states. To serve this market, “mine-mouth” power plants have been built, although air quality and the transmission lines themselves have raised environmental concerns

Uranium is also mined in the United States. The Energy Information Agency reports that “yellowcake” (an oxide with 91.8 percent uranium) production was 2,300 short tons in 1999 (EIA, 1999d). Overall, nuclear generation produces about 20 percent of the country’s electric power (EIA, 1999b). Because the United States is not currently building new nuclear power facilities and because power generation is expanding, uranium’s share of electric power generation is likely to fall in the near term. In the longer run, however, the use of uranium in power generation may increase, particularly if the United States seriously attempts to reduce its carbon dioxide emissions. In a recent article in Science, Sailor et al. (2000) presented a scenario in which the global carbon dioxide emissions would remain near their present values in 2050, but only by increasing nuclear power generation more than 12-fold

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The three mining sectors (metals, coal, and industrial minerals) have some common needs for new technologies; other technologies would have narrower applications; and some would be for unique or highly specialized uses. Metal mining can include the following components: exploration and development, drilling, blasting or mechanical excavating, loading, hauling, crushing, grinding, classifying, separating, dewatering, and storage or disposal. Separation may be by physical or

chemical means, or by a combination of processes; dewatering may be by thickening, filtering, centrifugation, or drying. Storage of metal concentrates may be open or enclosed; disposal of waste products is ordinarily in ponds or dumps. Treatment beyond crushing may be by wet or dry methods; if the latter, dust control is necessary. Classification is usually thought of as discrimination based on size, although with the use of a medium (usually water or air) particles can be differentiated to some degree by mass, or even by shape

Mining of industrial minerals may include several of the unit operations listed above, but the largest sector of this type of mining (the production of stone, gravel, and sand) seldom requires separation beyond screening, classification, and dense media separation, such as jigging. Other industrial mineral operations require very sophisticated technologies, even by metal-mining standards, to obtain the high quality of certain mineral commodities

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The most common mining methods used by surface coal mines are open pits with shovel-and-truck teams and opencast mines with large draglines. In underground coal mining, the most common methods are mechanical excavation with continuous miners and longwall shearers. Some coals, mostly coals mined underground, may require processing in a preparation plant to produce marketable products. Crushing and screening are common, as are large-scale gravity plants using jigs and dense-media separators, but flotation is not always attractive because of its costs and the moisture content of the shipped product. Coal and coal-bed methane are combustible and sometimes explosive. Therefore, deliberate fine grinding is avoided until just before the coal is burned

Although the mining industry dates back thousands of years, the industry’s technology is quite modern, the result of both incremental improvements and revolutionary developments. Although a miner or explorer, say, 75 years ago might recognize some of the equipment and techniques used today, many important changes have occurred in equipment design and applications. Trucks, shovels, and drills are much larger; electricity and hydraulic drives have replaced compressed air; construction materials are stronger and more durable; equipment may now contain diagnostic computers to anticipate failures; and such equipment usually yields

Although incremental improvements have driven much of this progress, major contributions have also come from revolutionary developments. Some examples of revolutionary developments in mining are the use of ammonium-nitrate explosives and aluminized-slurry explosives, millisecond delays in blast ignition, the global positioning system (GPS) in surface-mine operations, rock bolts, multidrill hydraulic jumbos, load-haul-dump units, safety couplers on mine cars, longwall mining, and airborne respirable dust control. In plants there are radiometric density gauges, closed-circuit television, hydrocyclones, wedge-bar screens, autogenous and semiautogenous grinding mills, wrap-around drives, high-intensity magnetic separators, spirals and Reichert cones, high-tension separators, continuous assay systems, high-pressure roll grinding, computerized modeling and process control, and many more innovations. The increase in productivity in the past several decades made possible by new technologies has far exceeded the average increase for the U.S. economy as a whole

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The goals of the IOF program, namely improving energy efficiency, reducing waste generation, and increasing productivity, present both challenges and opportunities for mining. Exploration normally requires very little energy. However, some exploration techniques, such as satellite remote sensing, require space flights, which require prodigious amounts of energy. Reducing waste generation suggests that more waste be left underground, and this is already being done to a considerable extent in the underground metal-mining sector by returning tailings mixed with cement underground as fill. If in-situ mining is considered as a means of reducing waste, the site-specific nature of this method and its potential environmental effects must be taken into account. Increasing productivity will require increasing output or reducing input, or both

The IOF progam has identified potential areas for improvements in mining. Some enabling tools are already available: sensors, ground-penetrating radar, GPS, and laser measuring techniques. Possible applications in surface and underground mining and milling operations include autonomous robotic equipment, technologies that can “look ahead” of the working face, safer and faster rock bolting closer to the face, and mechanical excavators or drill-blast-load units capable of working close to the face while keeping personnel away from dangerous situations

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