Surface mining is used for an estimated 40% of coal production. Used machinery equipment can be used to extract coal. Extracting coal is less expensive if it’s found near the surface. Once coal is extracted, the topsoil is then replaced and native trees and vegetation is planted to restore the original condition. There are three different types of surface mining: contour, strip, and mountaintop removal mining.
1- Contour Mining: Contour Mining is most commonly used in areas that have steep or rolling terrain. It involves digging the earth above the coal supply function from profit line, or coal seam, along the contours of the hilly terrain. This method can be dangerous because it may cause landslides and erosion problems.
2- Strip Mining: Strip Mining usually occurs on flat terrain. The earth is dug up in long cuts or strips until the coal seam is exposed. After the strip has been drilled and blasted and all the coal has been removed, a new strip is created right next to it and the process continues.
3- Mountaintop Removal Mining: Mountaintop Removal Mining involves using a combination of Contour Mining industrial machinery suppliers and Strip Mining. The mountaintops are removed to expose the coal beneath and the coal is extracted.
Underground Mining Methods
If the coal seams are too deep underground, then deep underground mining is necessary. Deep underground mining methods include Continuous, Longwall, Blast, Retreat Mining and Shortwall Mining.
o Continuous Mining: A machine that has a large rotating steel drum with tungsten carbide teeth scrapes coal from the seam. Conveyors are used to transport the removed coal. About 5 tons of coal can be mined per minute. Accounts for about 45% of underground coal production.
o Longwall Mining: A sophisticated machine that has a rotating drum that mechanically moves back and forth along the seam. Loosened coal falls on the pan line which takes the coal to the conveyor belt. Accounts for about 50% of coal production.
o Blast: An older mining method that uses dynamite and explosives to break away the coal seam. Accounts for less than 5% of coal production.
o Retreat Mining: One of the most dangerous coal mining methods. Pillars are used to hold up the mine roof as coal is extracted. The pillars collapse as miners retreat.
o Shortwall Mining: Similar to longwall mining. Uses a continuous mining machine with moveable roof supports. The machine shears coal panels about 200 feet wide and half a mile long.
