Isocoversional kinetic analysis of combustion and pyrolysis of municipal sewage sludge

In this study, the thermal behaviours of sewage sludge were carried out by thermal analysis under air and argon atmospheres in the range from ambient temperature to 800 °C. The studied materials were characterized in terms of their chemical composition (C, N, H, S and trace elements) and calorific value. The important results focus on the temperature of maximum weight loss rate and the effect of atmosphere (air, argon) and heating rate (5, 10, 20 and 40 °C). TG and DTG curves were analysed. Non-isothermal kinetic analysis was used to evaluate the Arrhenius activation energy and the pre-exponential factor. The kinetic parameters were calculated using three isoconversional methods: Friedman, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa. The isoconversional methods were used to find dependency of the activation energy of studied processes on the conversion degree. The average values of activation energy for sewage sludge combustion e.g. S_A are Ea = 146.72; 151.87; 148.88 kJ/mol calculated by Friedman, FWO and KAS methods, respectively. For all studied sewage sludge samples the slight differences between the values of activation energies obtained by Friedman, FWO and KAS methods were obtained.