Carbonization of coal-tar pitch under controlled atmosphere—Part I: Effect of temperature and pressure on the structural evolution of the formed green coke Original Research Article

The carbonization of an industrial coal-tar pitch was studied, by using a tube bomb, as a function of carbonization temperature (520 °C–580 °C) and inert gas pressure (1–20 bar) and resultant green cokes were evaluated according to yield and observation under polarized light microscopy. At 520 °C, green cokes present large isotropic domains as well as Brooks and Taylorʹs spheres whatever the pressure applied, indicating that the pyrolysis duration seems to be too short to obtain an entirely anisotropic texture. When carbonization temperature increases, samples present an entirely anisotropic texture. An increase of carbonization pressure from 5 to 10 bar leads to a sharp increase of the coke yield and of the uniaxial arrangement, this latter being progressive with increasing pressure at 550 °C and appearing only at pressures greater than 15 bar at 580 °C. Carbonization temperature and pressure are intimately correlated. The temperature increase involves a higher solidification rate, whereas the pressure increase delays the volatile departure and consequently the solidification rate. It is necessary to obtain a compromise between them so as to produce green cokes with oriented uniaxial texture.