Effect of Calcined Coke Size on Pitch Pyrolysis Behavior

Pitch coking determines the quality of pitch coke, which ultimately affects the quality of a carbon anode. In this work, green carbon anodes were studied by scanning electron microscopy (SEM), and the pitch pyrolysis process was tested using a custom-built pyrolysis device. The influence of the coke size on pitch pyrolysis was examined and the action law was analyzed. The results show that the outermost layer of the large size coke has a certain pitch thickness, the subouter layer is filled with a "mixture of fine particles and the pitch," and the internal area is not soaked by the pitch. Meanwhile, the small particles are soaked and wrapped by the pitch. The pyrolysis dynamics analysis shows that with the increase in particle size, the activation energy gradually increases to 70.00 kJ/mol for 1-2 mm, then rapidly decreases to 31.88 kJ/mol for 3-4 mm, and finally slowly increases to 50.56 kJ/mol for 6-9 mm. When the particle size increases, the coke size <0.5 mm area is dominated by a specific surface area, the 0.5-2 mm area is mainly regulated by a combination of a specific surface area and a porous structure, and the >2-3 mm area is dominated by the porous structure.