A dark or dark brown viscous liquid produced in the dry distillation of a coal with a pungent odor. Referred to as tar. Coal tar can be divided into low temperature coal tar, medium temperature coal tar and high temperature coal tar, and coal tar in coke production belongs to high temperature coal tar. It is one of the purifying products of coke oven gas which is condensed and separated in the process of crude gas cooling.

The properties and compositions of the medium and low temperature coal tar and the high-temperature coal tar are obviously different and should be processed separately. The medium and low temperature coal tar can be used to produce diesel oil, gasoline engine fuel oil and chemicals for waiting.

It is difficult to hydrogenation of high temperature coal tar to fuel oil, in accordance with traditional processing technology, high temperature coal tar fractions are further processed to separate a variety of chemical products.