Abstract: The pyrolysis kinetic of tobacco stem waste(TSW) was investigated by using single reaction model and three-parallel-reaction (TPR) model via thermogravimetric analysis(TGA). In single reaction model, the reaction mechanism of TSW pyrolysis presented as 14th order reaction f(α)=(1-α)¹⁴, with the apparent activation energy of 182.4 kJ/mol. According to the energy compensation effect results, the pyrolysis process of TSW could be divided into three stages which successively covered the conversion range of α=0-0.32, α=0.32-0.80, α=0.80-1 with the pre-exponential factor of 2.88×10¹⁰, 4.33×10¹⁴ and 9.76×10¹⁶, respectively. The single reaction model could not describe the pyrolytic mechanism of TSW reasonably. And then, the pyrolytic kinetic of TSW was investigated by using mixture Weibull distributed activation energy model(DAEM). Results showed that the mix-Weibull DAEM fitted the experimental data very well with correlation coefficients of R²≥0.997 6. According to the results of mix-Weibull DAEM, the apparent activation energy of three pseudo components followed the order of E₀(lignin, 195.26 kJ/mol)>E₀ (cellulose, 152.54 kJ/mol)> E₀(hemicelluloses, 121.18 kJ/mol). The pyrolytic mechanism for pseudo hemicelluloses was first-order reaction f(α)=1-α. And nucleation mechanism could be used to explain the pseudo cellulose pyrolysis. Order-based reaction mechanism was also suitable for pseudo lignin pyrolysis, however, the reaction order was between 3-4, which indicated that the pyrolytic mechanism of pseudo lignin was complex and might be a multiple steps reaction.

Key words: tobacco stem waste, thermogravimetric analysis, pyrolysis kinetics, Weibull distribution