Coal is the most abundant and widely distributed fossil fuel on the earth. The main elements of coal organic matter are carbon, hydrogen, oxygen, nitrogen and sulfur, in addition, there are very small amounts of phosphorus, fluorine, chlorine and arsenic and other elements.

The use of coal is very extensive, can be summarized into three main uses according to its purpose of use: thermal coal, coking coal, coal chemical industry coal, mainly including gasification coal, low temperature dry distillation coal, hydroliquefaction coal and so on.