Abstract
In this study, a thermogravimetric analysis of pyrolysis of sewage sludge (SS) obtained from physio-chemical wastewater treatment plant treating wastewater from the edible oil industry was performed. Thermogravimetric experiments were performed in a temperature range of 30–900 °C under inert atmosphere at three different heating rates: 10, 20 and 30 °C/min. Various parameters were analysed in the feedstock and in the produced biochar, including proximate and ultimate analysis. FTIR analysis was used to study the chemical changes in the materials before and after pyrolysis. Two different kinetic models were applied in the kinetic analysis, the Flynn–Wall–Ozawa model (FWO) and the Kissinger–Akahira–Sunose (KAS) model. In addition to the kinetic parameters, thermodynamic parameters were also calculated. Based on the experimental data and kinetic analysis, the potential of SS for use in the pyrolysis process was evaluated. The results of proximate and ultimate analysis of biochar showed an increase in ash and sulfur content and a decrease in volatile matter, carbon, nitrogen, hydrogen, oxygen content and calorific value. FTIR spectra showed significant changes in chemical bonds and functional groups in the pyrolyzed sample. The activation energy ranged from 49 to 352 kJ/mol ??for the KAS model and from 56 to 365 kJ/mol for the FWO model. The FWO and KAS kinetic models were found to be suitable for describing the pyrolysis of SS, as they exhibited high R2 values. The correlation coefficients for the KAS model were > 0.88 and for FWO > 0.91. The relatively high calorific value of SS shows its promising potential for energy recovery by pyrolysis.
