Non-isothermal kinetic analysis of sewage sludge from wastewater treatment plant

The thermal decomposition kinetics of sewage sludge was investigated by means of non-isothermal TG at different heating rates of 5 K·min⁻¹, 10 K·min⁻¹, 15 K·min⁻¹, 20 K·min⁻¹ and 30 K·min⁻¹. The non-isothermal kinetic parameters and mechanical functions were analyzed by means of Flynn-Wall-Ozawa equation and Coats-Redfern equation. Before and after DTG peak, Flynn-Wall-Ozawa and Coats-Redfern were used to determine the kinetic parameters. Before and after DTG peak, Eα→0=102.17 kJ·mol⁻¹, 88.17 kJ·mol⁻¹ respectively. Before DTG peak, the most probable kinetic function was No.3 G-B Equation, and the corresponding mechanism was controlled by Three-Dimensional Diffusion (cylindrical symmetry). The apparent activation energy and the pre-exponential constant (A) were Eβ→0=107.44KJ·mol⁻¹, lnAβ→0=12.64 respectively. After DTG peak, the most probable kinetic function was No.13 Avrami-Erofeev Equation (n=4), and the corresponding mechanism was controlled by random nuclear producing and growing process. The apparent activation energy and the pre-exponential constant (A) were Eβ→0=88.34 KJ·mol⁻¹, lnAβ→0=14.25 respectively.