The vacuum residue of petroleum is cracked and coked in a coking unit at 500 - 550℃ to generate black solid coke. It is generally considered as an amorphous carbon body, or a kind of highly aromatized polymer carbide, which contains acicular or granular carbon bodies with micrographite crystal structures. The carbon-hydrogen ratio is very high, ranging from 18 to 24. The relative density is 0.9 - 1.1, the ash content is 0.1% - 1.2%, and the volatile matter is 3% - 16%.