Pyrolysis model of pitch

Pitch is one of the most important precursors of the carbon materials. A deep understanding of the carbonization behaviors is helpful to better controlling the performances of the final products. Three partly overlapping temperature stages from the DTG curve of pitch were obtained by peak separation. Three series reactions of three pseudo-compositions were proposed to model them. The result shows that pyrolysis in each stage is first-order reaction. The calculated TG curves agree well with experimental data when the heating rate are increased from 2.5 K/min to 10 K/min. The dynamic of bubble growth caused by the volatiles during pyrolysis of pitch was theoretically calculated. It indicates that with the increase of heating rate, the diameter of bubble monotonously increases. The mass loss rate of pitch is the controlling factor to the bubble growth. The radical velocity of liquid around the bubble rapidly increases with heating rate at the medium temperature of the pyrolysis. It suggests that the heating schedule should be programmed as low rate in the medium temperature stage but high rate in the other temperature stages.