Coal, a kind of fossil fuel, is a solid combustible mineral that has formed from plant remains accumulated and buried in the geohistorical period through complicated biochemical activities and a series of geological actions. It is a mixture of macromolecular organic compounds and mineral matter. After burning, most of the mineral matter in the mixture will become ash. Generally, the mixture with the ash content less than 40% is called coal; if its ash content is over 40%, then it is called carbonaceous shale.
Coal is an important energy mineral, particularly in China. Since coal constitutes 75% of the total primary energy , it has occupied a pivotal position. Besides, coal is an important raw material for metallurgical and chemical industries. Therefore, the coal industry is a basic industry in the national economy. |
