Variation characteristics and adaptability of kinetic parameters of sludge pyrolysis in a self-designed FR-TGA

The kinetics models for the pyrolysis of sewage sludge that are based on conventional thermogravimetric analyzers are not effective in predicting the pyrolysis behavior of sludge at higher heat-mass transfer rates. Therefore, to this end, a more robust and adaptive model is needed. In the present study, a self-designed fast-reaction thermogravimetric analyzer (FR-TGA) was used to investigate the pyrolysis characteristics of sewage sludge and the influence of kinetic triplets. Based upon the results, a more accurate and reliable kinetic model was established. Results indicated that sludge pyrolysis at high heat-mass transfer rates showed lower apparent activation energy. Compared with the heating rate, the apparent kinetic parameters were more sensitive to the content of moisture in sludge. Moreover, moisture could significantly promote the pyrolysis reaction. Coupled with the mechanism of diffusion effect, a two-stage kinetic model was established, which could predict the pyrolysis process of sludge particles at high heat-mass transfer rates. The kinetic model and the behavior of various parameters could provide a reference for predicting the fast pyrolysis of sludge under different conditions.