Petroleum coke is a widely used carburizer at present.

Petroleum coke is a by-product obtained from refined crude oil. Residual oil and petroleum asphalt obtained from crude oil through atmospheric distillation or vacuum distillation can both be used as raw materials for manufacturing petroleum coke, which is then coked to produce green petroleum coke. The output of green petroleum coke is approximately less than 5% of the amount of crude oil used. The annual output of green petroleum coke in the United States is about 30 million tons. Green petroleum coke has a high impurity content and cannot be directly used as a carburizer; it must first undergo calcination.

Green petroleum coke comes in varieties such as sponge-like, needle-like, granular, and fluid.

Sponge petroleum coke is produced by the delayed coking process. Due to its high sulfur and metal content, it is usually used as fuel during calcination and can also serve as a raw material for calcined petroleum coke. Calcined sponge coke is mainly used in the aluminum industry and as a carburizer.

Needle petroleum coke is produced by the delayed coking process using raw materials with high aromatic hydrocarbon content and low impurity content. This type of coke has an easily breakable needle-like structure, sometimes referred to as graphite coke, and after calcination, it is mainly used in the manufacture of graphite electrodes.

Granular petroleum coke is in the form of hard granules. It is produced by the delayed coking process using raw materials with high sulfur and asphaltene content, and is mainly used as fuel.

Fluid petroleum coke is produced by the continuous coking process in a fluidized bed. It is in the form of fine granules with a non-directional structure, high sulfur content, and low volatile matter.