Needle coke is a type of coke that exhibits significant anisotropy from both its macroscopic and microstructural properties. It is named so because its particles, after crushing, are slender, needle-like in shape. This anisotropy reflects a high degree of order in its molecular structure, resulting in excellent graphitization.
For example, a type of coal-tar pitch-based needle coke, after graphitization at 2800°C, exhibits an interlayer spacing (DOM) of 33.57 nm and a graphitization degree of 96.5%. Needle coke also offers a range of advantages, including low thermal expansion, low porosity, low sulfur content, low ash content, low metal content, and high electrical conductivity. Its graphitized products exhibit excellent chemical stability, corrosion resistance, high thermal conductivity, and excellent mechanical strength at both low and high temperatures.
Needle coke, a high-quality carbon raw material that has been vigorously developed since the 1970s, is primarily used to produce high-power (HP) and ultra-high-power (UHP) graphite electrodes, as well as specialty carbon products for electric furnace steelmaking. It can also be used to produce high-quality brushes, batteries, steelmaking recarburizers, and high-temperature refractory materials. Using HP or UHP electric furnaces for steelmaking can shorten smelting time by 30% to 50% and save 10% to 20% of electricity, resulting in significant economic benefits.
Research on needle coke in my country began in the 1980s. From 1979 to 1985, institutions such as the Sinopec Research Institute of Petrochemical Technology conducted relentless process research and technological development on oil-based needle coke, while the Sinosteel Anshan Thermal Energy Research Institute researched coal-based needle coke.