Solar pyrolysis of waste biomass: Part 2 kinetic modeling and methodology of the determination of the kinetic parameters for solar pyrolysis of sewage sludge

Biomass pyrolysis is a fundamental thermal conversion method that has both industrial and economic potential. A deep knowledge of the pyrolysis character can give dramatically rise to the general development of thermal conversion methods for the effective use of biomass fuel in the incoming future. In this work, kinetic parameters estimation methods and methodology for sewage sludge pyrolysis has been presented. Special emphasis was put into combined use of the latest isoconversional methodology and model-fitting kinetics. The kinetic parameters estimation was based on a series of experiments using thermogravimetric analysis carried out for heating rates 20, 30 and 40 K/min. Complimentary use of model-based and isoconversional approach along with statistical analysis of both methods results has been presented. The proposed methodology, based on Friedman isoconversional kinetic parameters, E_α 31.4–244.9 kJ/mol and A_α 1.17–14.4 log(1/s), as initial guess values for optimization resulted in 10 independent reactions kinetic model, evaluating sewage sludge pyrolysis with R² > 0.999 with activation energies E∈<30.34; 259.7> kJ/mol, pre-exponential factors A∈<1.17; 22.49> log(1/s) and reaction orders n∈<1.17; 3>. Isoconversional methodology resulted in excellent conversion rate and mass loss fit while the order-based kinetic model simultaneously gave insight into theoretical 10 elementary sludge decomposition rates.