Production of Bio-oil by Oxidative Pyrolysis of Sewage Sludge in Rotating Fixed Bed Reactor

Pyrolysis is an attractive thermal conversion technology used to produce bio-oil and some chemicals. In this study, we investigated the pyrolysis of sewage sludge under N2 and CO2 atmosphere at various temperatures (350-750°C) in a rotating fixed bed reactor. For under N2 atmosphere, thermal gravimetric analysis (TGA) shows two major reaction peaks centered at 300 and 500°C. However, if CO2 was used instead of N2, the reaction rate at 300°C increased by 40%, and the peak at 500°C was significantly shifted to 425°C with the increasing reaction rate of 8-10%. The components in bio-oil obtained from inert and oxidative pyrolysis were identified. The typical characteristics of bio-oil from inert pyrolysis are mainly oxygenated and nitrogenated of aliphatic compounds, and also a little amount of alicyclic and aromatic compounds. If the pyrolysis temperature was increased, more aromatics compounds were obtained. Under CO2 or oxidative pyrolysis, it was found that the amount of aromatic compounds in the bio-oil was also increased while unsaturated and alicyclic compounds were decreased, which is possibly due to the enhancement of polymerization and cyclization by CO2. Moreover, where compared with under N2 atmosphere, the total bio-oil production was improved by 25% under an oxidative pyrolysis condition.