Coal Breaker - The Coal Breaking Process

The Coal Breaking Process

Ideally, coal breakers were placed so that the top of the breaking plant was equal to or slightly below the mine mouth so that gravity would move the coal to the breaking plant. Where this was not possible, coal would be hoisted to the top of the coal breaking plant. A boiler and boilerhouse would be located nearby to provide power for the hoist, moving screens, jigs, and crushers (although in more modern times this is supplied by electricity), along with an engine house (to house the engine for the hoist), pumps and pumphouse (to supply the coal washing machines with water), and headframe (for the hoist). The typical coal breaking plant was often eight or nine stories tall, sometimes rising 150 feet high or more.

In the typical coal breaking plant at the beginning of the 20th century, the coal entered the plant at the upper floor and slid down a gently inclined "picker table" where breaker boys removed obvious impurities such as rocks and large pieces of slate and threw them down chutes to the culm pile. The breakers also removed obviously clean lumps of coal and sent them down a separate "clean coal" chute for crushing. Lumps intermixed with impurities would go down a third chute for crushing and further cleaning.

On the second level of a typical breaker, coal would be roughly sorted. The fuel would move over sorting bars, with the various sizes of coal going down different chutes. Each type of roughly sorted coal would next pass over a "slate-picker screen" (sometimes called a "mud screen"), with the generally round coal falling through the screen and the flat slate passing over the screen to fall down a chute to the culm pile. Coal passing through the slate-picker screen would then be sorted by additional screens. Some these second screens were composed of flat iron perforated by holes of larger size toward the rear (where the coal entered) and smaller holes toward the front. These flat screens were sometimes shaken back and forth (hence the name "shaking screens"), which not only removed dirt and sulphur from the coal but broke down larger lumps of coal into smaller sizes and sorted it for further cleaning and processing. Other screens were cylindrical, making 10 revolutions per minute and performing the same function as shaking screen. Flat and cylindrical screens could be single-jacketed (a single screen) or double-jacketed (two screens, the first or inner screen having larger openings while the second screen had smaller ones).

The third level from the top was the crushing level. Most coal was still lump coal at this stage, and needed to be crushed in order to create smaller, more marketable product. Here, a series of interlocking, toothed crushers or rollers would break lump coal into progressively smaller sizes.

On the fourth level down, the coal was further cleaned of impurities. This was originally done primarily by hand, but hand picking was gradually supplanted after 1910 by improved screens and jigs. Although breaker boys worked at all levels of the coal breaker, most of the removal of impurities by hand occurred on this level. (Some picking did occur on the ground level of the coal breaker, where boys would locate good pieces of coal in the culm and return it to the "clean" coal stream.) Some coal might travel to this level directly from second level, if small enough, as at this level the screens and jigs were only capable of handling egg-grade coal and smaller. This area of the coal breaker was also where most dry screens and wet jigs operated. At this level, the use of conveyor belts (with or without paddles or scoops) was necessarily in order to move the smaller grades of coal, with most belts moving at about 33 feet per minute for pea coal and 50 feet per minute for larger grades. Multiple sorting and picking levels might exist in a single coal breaker, depending on the amount of coal to be processed.

Coal and culm were received at the ground level. Dry culm was taken away from the coal breaker by conveyor belt or rail car and dumped nearby. Very fine dry culm was sometimes separated from the heavier culm by forced air and blown through tubes to a separate pile. Wet culm was generally held in settling tanks or behind a coal slurry impoundment dam to allow particulate to settle out of the water. The "clean" coal, emerging from the coal breaker already sorted into its respective sizes, was collected primarily by rail cars and then delivered to market.