How We Mine
Coal mining operations commonly use several techniques to extract coal from the ground. The most appropriate technique depends upon coal seam characteristics such as geology and recoverable coal reserves. Drill hole data is used initially to define the size, depth and quality of the coal reserve area before committing to a specific extraction technique.
Underground mining techniques include continuous mining and longwall mining, while surface operations typically use truck-and-shovel mining to remove coal from the mining area.
Mined land is reclaimed for productive use as vacation areas, wildlife habitat, rangeland and farmland.
Once coal is mined, it is crushed and sized and may be washed in preparation plants where the product consistency, heat content and other quality characteristics are improved. This process involves removing impurities and possibly blending it with other coal to match customer specifications.
Patriot uses all of these techniques across its operations.
Continuous mining is an underground mining method that uses a room and pillar mining system. Coal is removed in a series of 18-20 foot wide areas, leaving columns or pillars to help support the roof. Pillars may later be extracted to maximize the reserve recovery. Shuttle cars or other similar equipment transport coal from the continuous miners at the face to a conveyor belt for transport to the surface.
Continuous miners are highly productive, remote-controlled and designed for a variety of seams and mining conditions.
The following diagram illustrates our typical underground mining operation using continuous mining techniques:
Longwall mining is an underground mining method that uses hydraulic shields, varying from five feet to 12 feet in height, to support the roof of the mine while a shearing machine traverses the coal face removing a two to three foot slab of coal with each pass. An armored face conveyer then moves the coal to a standard deep mine conveyer system for delivery to the surface.
Continuous mining is used to develop access to long rectangular panels of coal, which are then mined with longwall equipment, allowing controlled subsistence behind the retreating machinery.
The following diagram illustrates a typical underground mining operation using longwall mining techniques:
The surface mining method uses large electric or diesel-powered shovels or draglines to remove overburden, or heavy rock covering the coal, which is used to backfill pits after coal removal. Shovels load coal into haul trucks for transportation to the preparation plant or transportation loading facility. Productivity depends on equipment, geological composition and the ratio of overburden to coal.