Coal

Formation

At various times in the geologic past, the Earth had dense forests in low-lying wetland areas. Due to natural processes such as flooding, these forests were buried underneath soil.

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Early uses as fuel

The earliest recognized use is from the Shenyang area of China 4000 BC where Neolithic inhabitants had begun carving ornaments from black lignite.[20] Coal from the Fushun mine in northeastern China was used to smelt copper as early as 1000 BCE.[21] Marco Polo.

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Coking coal and use of coke

Coke is a solid carbonaceous residue derived from low-ash, low-sulfur bituminous coal (metallurgical coal), from which the volatile constituents are driven off by baking in an oven without oxygen at temperatures as high as 1,000 °C (1,832 °F), so the fixed carbon and residual ash are fused together.

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Refined coal

Refined coal is the product of a coal-upgrading technology that removes moisture and certain pollutants from lower-rank coals such as sub-bituminous and lignite (brown) coals. It is one form of several precombustion treatments and processes for coal that alter coal's characteristics before it is burned.

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Production of chemicals

Coal is an important feedstock in production of a wide range of chemical fertilizers and other chemical products. The main route to these products is coal gasification to produce syngas.

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Environmental effects

Despite significant economic benefits of using coal as fuel a number of adverse health,[81] and environmental effects of coal burning exist,[82] especially in power stations, and of coal mining.

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