Co-pyrolysis behaviors and kinetics of sewage sludge and pine sawdust blends under non-isothermal conditions

Mixing of sewage sludge with classical biomass, such as pine sawdust, can compensate the weaknesses of one fuel by another. The pyrolytic characteristics of sewage sludge (SS), pine sawdust (PS), and their blends were investigated under nitrogen atmosphere by dynamic thermogravimetric analysis at three heating rates of 10, 20, and 30 K min(-1). Three thermal stages (dehydration, devolatilization, further carbonization) were identified during the pyrolysis of single materials, as well as the blends. Blending of PS with SS can improve the devolatilizaion properties of SS, whereas the initial decomposition temperature increases with the increase in proportion of PS. It has been found that the pyrolytic characteristics of the blends can be estimated from those of parent fuels, suggesting that no significant synergistic effect existed during thermal degradation of PS/SS blends. The dependence of apparent activation energy on conversion obtained by Friedman method and distributed activation energy model (DAEM) revealed that the blends can be considered as multistage process. The results indicated that the DAEM can provide reasonable fits to the experimental data.