Coking gas is a by-product that comes from the coking ovens at a temperature of 900 °C. The gas is cooled and then cleaned. The aromatic hydrocarbons are removed from the gas with a washing agent. In a so-called light-weight-oil system, the aromatic hydrocarbons are separated from the washing agent and light-weight oil.

Light-weight oil (coal) is used in the chemical industry as a pre-product for the production of aromatic hydrocarbons benzene, toluene and xylene.