Petroleum coke is a flammable solid product obtained from petroleum residue and petroleum asphalt by coking. The color is black and porous, the main element is carbon, and the ash content is very low, generally below 0.5%. Petroleum coke is a kind of easy graphitized carbon, petroleum coke has a wide range of uses in chemical industry, metallurgy and other industries, and is the main raw material for the production of artificial graphite products and electrolytic aluminum carbon products.
According to the heat treatment temperature, petroleum coke can be divided into two kinds: raw coke and calcined coke. The former petroleum coke obtained from delayed coking contains a lot of volatile content and has low mechanical strength. The calcined coke is obtained by calcination. Most refineries in China produce only raw coke, and most calcination operations are carried out in carbon plants.
Petroleum coke can be divided into high sulfur coke (containing more than 1.5% sulfur), medium sulfur coke (containing 0.5%-1.5% sulfur), and low sulfur coke (containing less than 0.5% sulfur) three kinds, graphite electrodes and other artificial graphite products generally use low sulfur coke production.
Needle coke is a kind of high-quality coke with obvious fibrous texture, especially low thermal expansion coefficient and easy graphitization. When the coke block breaks, it can be split into slender strip particles according to the texture (the aspect ratio is generally above 1.75), and the anisotropic fibrous structure can be observed under the polarized light microscope, so it is called needle coke.
The physical and mechanical anisotropy of the needle coke is very obvious, and it has good electrical and thermal conductivity parallel to the long axis of the particles, and the thermal expansion coefficient is low. During extrusion molding, the long axis of most particles is arranged according to the extrusion direction. Therefore, needle coke is the key raw material for manufacturing high-power or ultra-high-power graphite electrodes, which have low resistivity, small coefficient of thermal expansion and good thermal shock resistance.
Needle coke is divided into oil needle coke produced from petroleum residue and coal needle coke produced from refined coal asphalt.
Coal tar pitch is one of the main products of coal tar deep processing. It is a mixture of a variety of hydrocarbons, black high viscosity semi-solid or solid at room temperature, without a fixed melting point, softened after heat, and then melted, with a density of 1.25-1.35g/cm3. According to its softening point is divided into low temperature, moderate and high temperature asphalt three kinds. The yield of medium temperature asphalt is 54-56% of coal tar. The composition of coal pitch is very complicated, which is related to the property of coal tar and the content of heteroatoms, and is also affected by the coking process system and the processing conditions of coal tar. There are many indexes to characterize the properties of coal pitch, such as asphalt softening point, toluene insoluble (TI), quinoline insoluble (QI), coking value and rheological properties of coal pitch.
Coal pitch is used as binder and impregnating agent in carbon industry, and its properties have great influence on the production process and product quality of carbon products. Binder asphalt generally uses medium temperature or medium temperature modified asphalt with moderate softening point, high coking value and high beta resin, and the impregnation agent should use medium temperature asphalt with low softening point, low QI and good rheology.
Post time: Feb-07-2025