Characterization of Bio-Oil Obtained from Sewage Sludge Pyrolysis Catalyzed by Char

The pyrolysis of sewage sludge(SS) in the presence of sewage sludge pyrolysis char(SSC) as catalyst was conduct in a horizontal reactor at 500 degrees C. Gas chromatography-mass spectroscopy (GC-MS), element analysis, high heating value (HHV) analysis, water content analysis and gel permeation chromatography(GPC) were used to characterize the pyrolysis oil. The declined char yields with increased SSC mix ratio (MR) indicated that SSC could promote the devolatilization reaction. Meanwhile the declined top phase oil (TPO) yield and increased bottom phase oil (BPO) and gas yield showed that crack reaction may happen catalyzed by SSC. According to the result of GC-MS, aliphatics and steroids content drops apparently since MR increased to 50 wt.%, while aromatic compounds and phenols content increased at the same time. Element analysis showed an apparent transportation of hydrogen and oxygen from TPO to BPO. HHV of TPO decreased with MR increased. The result of GPC indicated that increased MR caused continuing decreased average molecular weight of TPO. Consequently, the increased SSC addition could promote the devolatilization and large molecular compounds catalysis crack of sewage sludge.