2012年4月17日星期二

Three Methods Can Help You Achieve Mining Metals

Mining refers to the process of extracting metals and minerals from the earth. Gold, silver, diamond, iron, coal and uranium are just a few of the vast array of metals and minerals that are obtained by this process. In fact, mining is the source of all the substances that cannot be obtained by industrial processes or through agriculture. Mining reaps huge profits for the companies that own them and provides employment to a large number of people. It is also a huge source of revenue for the government. Despite its economic importance, the question that how does mining affect the environment is a pressing environmental issue.
Surface or open-pit mining requires extensive blasting, as well as rock, soil, and vegetation removal, to reach lode deposits. Benches are cut into the walls of the mine to provide access to progressively deeper ore, as upper-level ore is depleted. Ore is removed from the mine and transported to milling and beneficiating plants for concentrating the ore, and smelting, and/or refining. Open pit mining is the primary domestic source of iron, copper, gold, and silver.
Underground mining entails sinking a shaft to reach the main body of ore. 'Drifts,' or passages, are then cut from the shaft at various depths to access the ore, which is removed to the surface, crushed, concentrated, and refined. While underground mines do not create the volume of overburden waste associated with surface mining, some waste rock must still be brought to the surface for disposal. Waste rock may either be returned to the mine as fill or put in a disposal area. In the U.S., only lead, antimony, and zinc are solely underground operations.
Solution or fluid mining entails drilling into intact rock and using chemical solutions to dissolve lode deposits. During solution mining, the leaching solution (usually a dilute acid) penetrates the ore, dissolving soluble metals. This pregnant leach solution is then retrieved for recovery at a solvent extraction and electrowinning (SX/EW) plant. This method of mining is used in some parts of Arizona, Nevada, and New Mexico to recover copper. To a service-oriented brand integrity,As the professional manufacturer of complete sets of mining machinery ,like cone crushers, Henan Hongxing is always doing the best in products and service.
Historically, the primary mining method has been underground mining. However, with the advent in recent decades of large earth moving equipment, less expensive energy sources, and improved extraction and beneficiation technologies, surface mining now prevails in most industry sectors. Open-pit mining is generally more economical and safer than underground mining, especially when the ore body is large and the overburden (surface vegetation, soil, and rock) relatively shallow. In fact, the lower cost of surface mining has allowed much lower-grade ores to be exploited economically in some industry sectors.
The Indonesian government has sued a gold mining company for throwing away poisonous waste, such as arsenic and mercury, into the Buyat Bay. Fish in the bay was killed. People in the surrounding area can no more eat fish. They are already suffering from various illnesses like constant headache, skin rashes, tumors and breathing difficulty.
Effects of mining on the environment may not be evident immediately, they are usually noticed after some years. Although the developed countries have tight norms regarding mining, such rules can be easily flouted in countries which lack strict monitoring of the procedures being followed for mining. The effects in such cases can be devastating for the environment. Be it due to ignorance of the regulations or just a freak accident, incidents like the Guyana spill of 1995 may occur again. This highlights the fact that issues like how does mining affect the environment are worth some serious deliberation.

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