Effects of lipids on sludge and chlorella protein pyrolysis by thermogravimetry Fourier transform infrared spectrometry

Biomass pyrolysis has attracted attention; however, its development has been restricted by the formation of NOx precursors, which result mainly from protein pyrolysis. In addition, the effect of lipids on this process is not clear. We extracted proteins and lipids from chlorella and sewage sludge to investigate the thermal decomposition characteristics, thermodynamic properties, kinetic parameters, and reaction mechanisms of protein with or without lipids. Two model-free methods Flynn-Wall-Ozawa (FWO) and Friedman (FM) were used to calculate the kinetic energy. Between 150 and 600 ℃, the average activation energy (E) of sludge protein was 73.63 kJ/mol (FM) or 72.53 kJ/mol (FWO), whereas with lipids, it was 129.19 kJ/mol (FM) or 124.55 kJ/mol (FWO), indicating that lipids restrict the pyrolysis of sludge protein. There was no significant difference between E of chlorella protein pyrolysis with or without lipids. Moreover, the proteins in sludge and chlorella released less NH 3 under the influence of lipids; however, the formation of HCN was affected slightly. The results of this study provide a reliable reference for the regulation of protein pyrolysis, considering the production of NOx precursors.