Effect of carboids on the structure of pyrolysis cokes and on the properties of products made from them

Conclusions

• 1. The carboids contained in tars treated under two different sets of pyrolysis conditions have approximately identical dimensions, but different elementary composition and somewhat differing structures. This difference is confirmed by the fact that with the artificial enrichment of tar of exactly the same composition with carboids treated under mild and severe pyrolysis conditions, up to an amount of 8%, cokes with a different value of the pycnometric density (d_P= 2.05 g/cm³ and 2.02 g/cm³, respectively) and a different structure are obtained.

• 2. Independently of the severity of the pyrolysis conditions, tars not containing carboids yield a typical electrode coke with a predominantly striated structure and d_P= 2.10 g/cm³, which confirms the undoubted role of carboids in the formation of the typical structure of SPPC coke.

• 3. The results obtained confirm the insufficiency of d_P as an index to characterize cokes of the SPPC type, as well as of the characterization of the degree of preparation of a pyrolysis tar for coking only with respect to its content of the solid phase (carboids).

• 4. With an increase of the carboid content in a tar treated under mold pyrolysis conditions up to 8% (i.e., up to a value usually existing in the production of SPPC coke), the properties of graphitized samples prepared on the basis of coke from such a tar approach the properties of analogous samples prepared on the basis of SPPC coke.