Raw material characteristics of oil series needle coke

Needle coke is a porous solid with silver gray appearance, which has obvious fiber texture tendency, and is characterized by high crystallinity, high strength, high graphitization, low thermal expansion, low ablation, etc. It has special uses and important significance in national defense and civil industry, and is a high-quality raw material for manufacturing graphite electrodes, battery anode materials and high-end carbon products. 

According to the different production materials used, needle coke can be divided into oil series and coal series: needle coke produced with petroleum refining products as raw materials is called oil series needle coke, and needle coke produced with coal tar pitch and its distillate as raw materials is called coal series needle coke. The production of needle coke from petroleum products has obvious environmental advantages, low implementation difficulty and low production cost, and has been paid more and more attention.

Oil series needle coke can be divided into green coke and calcined coke. The green coke is used to produce various battery anode materials, and the calcined coke is used to produce high-power graphite electrodes. In recent years, with the increasingly severe environmental protection situation, new energy vehicles have been rapidly developed, driving the demand for battery anode materials; At the same time, iron and steel enterprises' backward converter was replaced by EAF (electric arc furnace). Under the dual effect, the market demand for needle coke has increased significantly. At present, the production of oil series needle coke in the world is dominated by American enterprises. In China, only a few companies such as Jinzhou Petrochemical, Jingyang Petrochemical and Yida New Materials have achieved stable production. High end needle coke products mainly rely on imports, which not only causes a lot of capital waste, but also is easy to curb. It has a great strategic significance to accelerate the research of needle coke production technology and achieve the goal of "first-class production" as soon as possible.

Raw materials are the key factor affecting the quality of needle coke. Suitable raw materials can greatly reduce the difficulty of mesophase pitch generation and eliminate subsequent unstable factors. Raw materials for needle coke production shall have the following characteristics:

• ① The aromatics content is high, especially the content of the linear 3 and 4 ring short side chains of aromatic hydrocarbons is 40%-50%. In this way, the aromatic hydrocarbons molecules are condensed to form larger planar aromatic hydrocarbons molecules during carbonation, and the large π bond electron cloud is superposition to form a relatively complete graphite-like structure lattice

• ② The content of asphaltene and gum existing in the molecular structure of polycyclic aromatic hydrocarbons is low. These substances have strong molecular polarity and high reactivity, and they are easy to condense with each other to form coke precursors during carbonization, without the opportunity to arrange each other. Therefore, it is generally required that the heptane insoluble matter is less than 2%.

• ③ The sulfur content shall not be greater than 0.6%, and the nitrogen content shall not be greater than 1%. sulfur and nitrogen in the production of electrodes are easy to escape by high temperature, resulting in gas expansion, which may cause cracks on the electrode.

• ④ The ash content is less than 0.05%, and there is no mechanical impurities such as catalyst powder. When carbonizing, the reaction will be carried out too fast, which will increase the difficulty of mesophase spheres generation and affect the properties of coke.

• ⑤ The content of vanadium, nickel and other heavy metals is less than 100ppm, because these metal compounds have catalytic effect, will accelerate the nucleation of mesophase pellets, making it difficult for the pellets to grow fully. At the same time, these metal impurities left in the products will cause problems such as voids and cracks, leading to the decline of product strength.

• ⑥ When the quinoline insoluble (QI) is zero, QI will attach around the mesophase, preventing the growth and fusion of spherical crystals. After coking, needle coke with good fiber structure cannot be obtained.

• ⑦ The density is greater than 1.0g/cm³ to ensure sufficient coke yield.

In fact, the raw oil that meets the above requirements is relatively rare. From the perspective of composition, catalytic cracking slurry, furfural extract oil and ethylene tar with high aromatic content are ideal raw materials for needle coke production. FCC slurry is one of the by-products of the catalytic unit, which is usually delivered as a cheap fuel oil. As it contains a large amount of aromatic components, it is a high-quality raw material for producing needle coke in terms of composition. In fact, the vast majority of needle coke products worldwide are prepared from FCC slurry. Welcome to consult us for future supply and demand analysis of needle coke and graphite electrode.