Coal Mining is Major Applying Field in Crushers

cost of iron mining process use giant machines to eliminate coal from the ground. They use two techniques: surface or underground mining. Many U.S. coal beds are extremely near the ground��s surface, and about two-thirds of coal production comes from surface mines. Contemporary mining methods permit us to effortlessly reach most of our coal reserves. Because of development in surface mining and improved mining technology, the amount of coal produced by one miner in 1 hour has greater than tripled since 1978.
Coal mining in the past started in the middle of the seventeen hundreds, in the state of Pennsylvania. Over the years, many ways to remove this substance from the earth have been used, with methods being classified as underground or surface. The reason that it was first mined from the earth was not for electricity, but to be used in steel mills. It was not until the eighteenth century that coal was used to generate electricity to light homes and businesses. The first miners used a method called room and pillar, and eventually this method was combined with a method termed retreat. Coal mining in the past depended on workers and supporting the mine walls and ceilings. Rooms were carved out of the mine, and these were supported by massive pillars and beams. Miners would remove the coal from these underground rooms. When retreat mining was done along with room and pillar, the rooms were collapsed as the miners retreated from the mine. This collapse opened up even more coal seams, which could then be recovered. It was not until the middle of the nineteen sixties that this process changed much. This is when longwall mining started being used. To a service-oriented brand integrity,As the professional manufacturer of complete sets of mining machinery, like flotation cell, Henan Hongxing is always doing the best in products and service.mechanical feeder:http://www.crusher-machine.com/n142.html
Coal mining in the past includes the longwall mining method as well. This method is much more effective, because a much larger percentage of the seam can be removed. This method uses a machine which carefully collapses a huge part of the room in a controlled manner, allowing a lot more of the seam to be accessed and removed. Surface mining can also be done if the seam is close to the surface. In this method the ground covering the coal seam is removed, then the coal is removed. The ground is put back down and seeded, to return the land back to the original condition. Unlike coal mining in the past, current mining operations do consider their environmental impact on the earth and surrounding areas, but this still does not negate the harmful effects that these operations can have. Coal is a fossil fuel which is not renewable, and it takes millions of years for this fuel to be created. Once it is gone it can not be replaced, and there are limited reserves left in the earth. Coal is mainly used to generate electricity in the United States, and when it is burned it releases large amounts of greenhouse gases and pollution. This causes damage to the environment and speeds up the global warming as well.
Underground mining, occasionally called deep mining, is utilized when the coal is buried several hundred feet beneath the surface. Some underground mines are 1,000 feet deep. To remove coal in these underground mines, miners ride elevators down deep mine shafts exactly where they run machines that dig out the coal.