The organic matter in coal is a complex macromolecular organic compound, which is mainly composed of carbon, hydrogen, oxygen, nitrogen, sulfur and phosphorus, and the sum of carbon, hydrogen and oxygen accounts for more than 95% of the organic matter. Inorganic substances in coal also contain a small amount of carbon, hydrogen, oxygen, sulfur and other elements. Carbon is the most important component in coal, and its content increases with the deepening of coalification. The carbon content in peat is 5% ~ 6%, lignite is 6% ~ 7%, bituminous coal is 74% ~ 92%, and anthracite is 9% ~ 98%. Sulfur in coal is the most harmful chemical component. 2.5% ~ 4% of sulfur-rich coal; 1.5% ~ 2.5% of medium sulfur coal; Low sulfur coal, 1.% ~ 1.5%; Ultra-low sulfur coal, less than or equal to 1%. Sulfur in coal can be divided into two categories: organic sulfur and inorganic sulfur.

Coal is an important energy source and an important raw material for metallurgical and chemical industries. It is mainly used for combustion, coking, gasification, low-temperature dry distillation, hydro-liquefaction, etc. ① Combustion. Coal is an important energy resource for human beings, and any coal can be used as industrial and civil fuel. ② Coking. Put coal in a dry distillation furnace and isolate it. Organic matter in coal is gradually decomposed with the increase of temperature, in which volatile substances escape in gaseous or vapor state and become coke oven gas and coal tar, while non-volatile solid residues are coke. Coke oven gas is a fuel and an important chemical raw material. Coal tar can be used to produce fertilizers, pesticides, synthetic fibers, synthetic rubber, paints, dyes, medicines, explosives, etc. Coke is mainly used for blast furnace ironmaking and casting. It can also be used to make nitrogen fertilizer and calcium carbide. Calcium carbide is a synthetic chemical product such as plastic, synthetic fiber, synthetic rubber, etc. ③ Gasification. Gasification refers to the transformation into gas that can be used as industrial or civil fuel and chemical synthesis raw materials. ④ Low-temperature carbonization. Low-temperature tar and low-temperature coke oven gas can be made by low-temperature carbonization of coal or oil shale at a temperature of about 55℃. Low-temperature tar can be used to make high-grade liquid fuels and as chemical raw materials. ⑤ Hydroliquefaction. Coal, catalyst and heavy oil are mixed together to destroy the organic matter in coal at high temperature and high pressure, which reacts with hydrogen to transform into low-molecular-weight liquid and gaseous products, and further processing can obtain liquid fuels such as gasoline and diesel. The main raw materials for hydroliquefaction are lignite, long-flame coal and gas coal.