Synergistic effects during co-pyrolysis of microalgal residues and municipal sewage sludge in an H2-containing atmosphere: Pyrolysis characteristic and kinetics

Abstract

In this study, the co-pyrolysis kinetics of municipal sewage sludge (MSS) and Chlorella vulgaris (MCV) in hydrogen atmosphere was studied by thermogravimetric analyzer. Three dynamic models (Friedman, Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose) and DAEM (a model fitting method) were used to accurately fit the experimental data at three heating rates (10, 30 and 50 °C/min). Their physical and chemical properties indicate that they have potential for energy recycling and fuel production. The kinetic model parameters are fitted successfully at different heating rates, and the linear fitting curve of DAEM is within the expectation. The kinetic curve fitting results show that the activation energy changes with the conversion rate, which is directly related to the complexity of molecular chain breaks during pyrolysis. When the proportion of MCV is 20 % (MSS80MCV20), the average activation energy of pyrolysis at 50 % conversion is the lowest, no more than 100 KJ/mol. This data is significantly lower than the average activation energies of the other three samples, which are 179 KJ/mol, 325 KJ/mol and 260 KJ/mol. This study confirmed that the mixed pyrolysis of MSS and MCV in hydrogen atmosphere can significantly change the activation energy Eα of the reaction, which can provide basic data support for the reaction operation conditions of the pyrolysis unit.