graphite electrode with top quality
Research on Needle Coke as Main Raw Material of Graphite Electrode
Needle coke is an important raw material for the preparation of high-power graphite electrodes (HP), ultra-high-power graphite electrodes (UHP) and other carbon products. It has low sulfur, low ash, high density, good electrical conductivity, easy graphitization and low thermal expansion coefficient. The significant advantage is that with the deepening of needle coke research, it is found that the nature of the raw material has an important impact on the quality of needle coke, especially the formation, growth and fusion of the mesophase. Therefore, the research on the raw material of needle coke is gradually Become the focus of needle coke research.
graphite electrode with top quality mesophase formation mechanism
In the preparation process of needle coke, the formation, growth and fusion of the mesophase are very important. Brooks and Taylor151 proposed the mesophase for the first time. In 1985, the International Committee on Carbon Characterization and Terminology officially named the mesophase formed in the carbonization system as carbon. Qualitative mesophase. A large number of scholars have supplemented and perfected the formation mechanism of the carbonaceous mesophase in the liquid phase carbonization theory, and laid the foundation for different intermediate mechanisms.
In the liquid phase carbonization theory, the formation mechanism of the mesophase is described as: as the temperature rises, the materials in the raw material undergo dehydrogenation condensation, cyclization, and aromatic ring formation to gradually form a large molecular weight aromatic ring fused ring molecular structure. Under the action of thermal motion, plane molecules are stacked in the vertical direction due to van der Waals force and intermolecular dipole moment to form colloidal particles 3F. Under the action of surface tension, a new phase of anisotropic, flowing, spherical liquid crystal is formed. ——Mesophase pellets (as shown in Figure 1), the pellets continuously absorb the aromatic molecules in the isotropic matrix from the pitch and gradually grow up. When the grown spheres come into contact, the flat molecules of each sphere insert and fuse each other to form a larger sphere (compound sphere), and form an intermediate phase after repeated fusion and collision.
Professor Mochida from Japan proposed the “microdomain construction” theory of the mesophase in the study of the formation mechanism of carbon fibers. He believed that the formation process of the graphite electrode with top quality mesophase is that the aromatic planar macromolecules first form regular flaky molecular stacking units. The molecular stacking unit forms spherical microdomains, and the microdomains are densely packed to form mesophase spheres, as shown in Figure 2. The ash particles, coke oven carbonization chamber refractory brick powder and metal powder are carried into the coal tar by the rising gas flow;