Solid fuel purposes, such as refining metals. Coal is the largest source of energy for the generation of electricity worldwide, as well as one of the largest worldwide anthropogenic sources of carbon dioxide releases. The extraction of coal, its use in energy production and its byproducts are all associated with environmental and health effects including climate change. Variations such as smokeless coal can be formed naturally in the form of anthracite, a metamorphosed type of coal with a very high carbon content that gives off a smokeless flame when set alight. Coke is a fuel with few impurities and a high carbon
Coal breaker 19th century and early 20th century led to the use of mechanical devices for separating impurities from coal in coal breakers. Screens and sorters were used for dry coal. Some examples from the beginning of the 20th century are: To handle wet coal, coal jigs were used. Coal jigs separated coal from impurities by using gravity. Since the relative density of uniformly sized pieces of coal, slate, ash, dirt, and sulphur vary, pieces of each element will descend through water at different speeds—allowing them to be separated. Some examples of coal jigs from the beginning of the 20th century include: