The quality of petroleum coke largely depends on the nature of the raw material and its processing conditions. The main quality indicators are:

Purity
Refers to the content of sulfur and ash in petroleum coke. High-sulfur coke will cause the product to swell during graphitization, resulting in cracks in the carbon product. High ash content will hinder the crystallization of the structure and affect the performance of carbon products.

Crystallinity
Refers to the structure of the coke and the size of the mesophase spheres. The coke formed by small spheres has a porous structure such as sponge-like, and the coke formed by large spheres has a dense structure such as fibrous or needle-like, and its quality is superior to that of sponge coke. In the quality index, true density roughly represents this performance, and high true density indicates good crystallinity.

Thermal shock resistance
Refers to the crack resistance of coke products when they are subjected to thermal shocks suddenly rising to high temperatures or rapidly cooled from high temperatures. The products of needle coke have good thermal shock resistance, so they have high use value. The coefficient of thermal expansion represents this property. The lower the coefficient of thermal expansion, the better the thermal shock resistance.

Graininess
The relative content of powdered coke and massive granular coke (usable coke) contained in the reaction coke. Most of the powder coke is broken by mechanical action such as extrusion friction in the process of decoking, storage and transportation, so its amount is also a manifestation of mechanical strength. The green coke can be prevented from being broken after being calcined to mature coke. The coke with more granular coke and less powder coke has higher use value.