When most people think of coal mining, they envision men in soot covered clothes and hard hats digging at deposits in deep underground caverns. These mental images commonly include coal cars rumbling on rails as they emerge from the earth, filled to the brim with rocky ore.
The world of modern, long-wall coal mining is a far different place. Yes, it's underground, the miners still wear hard hats, and the environment is filled with soot. However, today's mining operations are carefully monitored and the entire process is highly automated.
Three miles underground, a sophisticated, high-powered mining machine moves steadily through a six-foot-high tunnel at an average speed of two miles per hour, carving out coal, then conveying it to a crusher and carrying it to the surface.
Instead of digging out the ore, a long-wall mining system slices it from the exposed tunnel face, using giant rotating shears. The shorn coal tumbles onto a conveyer below the shears, and is conveyed to the “stageloader” where it is crushed and dumped onto the main conveyer belt that eventually hauls it out of the mine.
Integral to the long-wall shear and conveyor is a moving metal roof that protects it from the thousand plus feet of ground above. The ceiling panels automatically advance above the mighty shears, powered by hydraulic roof supports that stand on the other side of the tunnel-like soldiers, moving in a slow, sideways lock-step with the shears.
This complex and massive machine makes long-wall mining the most efficient and productive method for excavating coal. In fact, it produces 3,000 to 25,000 tons of ore per shift, versus 600 to 1,000 tons for the conventional or commonly used method known as room-and-pillar mining. Using that method, miners develop one section of a mine at a time after carving out load-bearing columns of coal to support the roof above their heads.
Long-wall mining also is considered safer than the room-and-pillar method, largely because the process is mostly automated, requiring fewer workers in this famously hazardous environment.
Still, long-wall mining has its drawbacks: The equipment is expensive and the mining conditions are harsh. An entire long-wall system can cost between $50 million and $100 million, while the electrical controls used to operate it can cost an additional $1 million to $2 million. These investments grind away all day, every day, in hot tunnels filled with coal dust.