Detailed description of graphite electrode raw materials
There are three types of raw materials for graphite electrodes: petroleum coke, needle coke and coal pitch.
Raw material – petroleum coke
According to the heat treatment temperature, it is divided into two types: raw coke and calcined coke.
According to the level of sulfur, it is divided into high sulfur coke (containing more than 1.5% sulfur), medium sulfur coke (containing sulfur 0.5%-1.5%) and low sulfur coke (containing less than 0.5% sulfur).
The production of graphite electrodes and other artificial graphite products is generally produced using low sulfur coke.
Sulfur is a harmful element, and the graphite electrode produced by petroleum coke with a large sulfur content produces a “flat” phenomenon during the graphitization process, which easily leads to product cracking. When graphite steel with high sulfur content is used for steelmaking, the consumption of steel per ton of steel has increased. The petroleum coke content of most of China’s producing areas is low. Only petroleum pyrophoric oil produced by refineries using domestic high-sulfur crude oil or imported high-sulfur crude oil is used. The score is higher.
Raw material – needle coke
Needle coke is a kind of high quality coke which has obvious fibrous texture and low thermal expansion coefficient and is easy to graphitize.
1.Oil needle coke: Produced from petroleum residue as raw material.
2.Coal-based needle coke: produced from refined coal bituminous raw materials.
The physical and mechanical properties of needle coke are very obvious. They are the key raw materials for the manufacture of high-power or ultra-high-power graphite electrodes. The graphite electrode produced has low resistivity, small thermal expansion coefficient and good thermal shock resistance.
Raw material – coke pitch
Coal pitch is one of the main products of coal tar deep processing and is a mixture of various hydrocarbons.
According to its softening point, it is divided into low temperature, medium temperature and high temperature asphalt.
Used as a binder and impregnating agent in the carbon industry. The binder asphalt generally uses medium or medium temperature modified asphalt with moderate softening point, high coking value and high β resin. The impregnating agent should use a lower softening point and a lower QI. Medium temperature asphalt with good rheological properties.