There are four classification methods for the petroleum coke used in the production of ultra-high power graphite electrodes
Petroleum coke is usually classified in the following four ways:
According to the coking method, it can be divided into delayed coke, kettle coke, fluidized coke and open-hearth coke. Currently, delayed coke is produced in large quantities at home and abroad, while kettle coke is only produced in small quantities.
According to the heat treatment temperature, it can be divided into two types: green coke and calcined coke (calcined coke). Green coke is prepared by delayed coking (500℃) and contains a large amount of volatile matter, with low mechanical strength. Calcined coke is obtained by calcining green coke (around 1350℃). Most domestic refineries only produce green coke, and calcination operations are mostly carried out in carbon plants.
According to the sulfur content of coke, it can be divided into high-sulfur coke, medium-sulfur coke and low-sulfur coke.
According to the appearance structure and performance of petroleum coke, it can be divided into three types: sponge-like coke, honeycomb-like coke, and needle-like coke.
Sponge-like coke has a sponge-like appearance, with a high content of impurities and many small pores inside. The coke walls between the pores are very thin, making it unsuitable as a raw material for the production of carbon materials. Honeycomb-like coke has a relatively uniform distribution of small pores inside, with a distinct honeycomb structure and good physical and mechanical properties. Such petroleum coke can be used as a raw material for the production of ordinary power graphite electrodes, prebaked anodes, and electrical carbon products. Needle-like coke has a distinct striped appearance, with pores inside the coke block arranged in a slender elliptical orientation, which break up into slender particles after crushing. It can be used as a raw material for the production of high-power and ultra-high-power graphite electrodes. Petroleum coke is a solid product obtained from coking various petroleum residues, petroleum asphalt, or heavy oil. Due to different coking methods, petroleum coke can be divided into delayed coke and kettle coke. Currently, the petroleum industry produces delayed coke, while kettle coke has been eliminated. Delayed coking is a process in which raw oil is converted into gas hydrocarbons, light and medium distillates, and coke through deep thermal cracking. Its raw material is generally a residue obtained from vacuum distillation of deep desalted crude oil. Sometimes, a certain proportion of thermal cracking residue or shale oil is also added to the vacuum residue. The quality of petroleum coke mainly depends on the nature of the residue, but is also affected by coking conditions.
