Manufacture of Synthetic Carbon

The raw materials utilized in the manufacture of carbon and graphite products can be divided into solids and binders. The following. solids are generally used  

Cokes are formed from the appropriate materials by liquid phase pyrolysis. More or less structured cokes are formed depending upon the pyrolysis conditions and the composition of the starting materials. The ease of graphitization increases with increasing crystallinity and with increasing crystallite size of the coke. Petroleum cokes are the preferred raw materials with well-ordered strongly anisotropic needle coke, a type of petroleum coke, being one of the most valuable raw materials. For some applications, however, isotropic cokes are used. Important quality criteria for the solids, other than crystallinity, are  

Addition of carbon black, anthracite and natural graphite improves certain properties. Anthracite is also used in the manufacture of carbon electrodes for economic reasons. 

The so-called green petroleum coke produced by delayed coking still contains volatile components, which escape at high temperatures, leading to excessive porosity and cracking. In addition form stability cannot be ensured. To avoid this it is first subjected to calcination in gas fired rotary kilns or rotary hearth kilns at 1300 to 1400°C. This is also necessary with anthracite, which can be calcined at even higher temperatures. 

The ratio of binder to solids is dependent on the one hand upon the particle composition of the solid, since all the particles have to be coated as homogeneously as possible, and on the forming process, to ensure a certain plasticity in the bulk. On the other hand the probability of firing faults increases with increasing binder content and thus a compromise has to be sought. 

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