BIO-OIL AND BIO-CRUDE GASIFICATION FOR SYNGAS PRODUCTION: ENERGY, EXERGY AND ENVIRONMENTAL ANALYSES

Abstract

Fast pyrolysis is a thermochemical process that converts solid biomass into bio-oil, biochar, and non-condensable gases. In this study, a simulation model was developed in Aspen Plus® using the Ranzi kinetic mechanism to describe biomass pyrolysis. Two gasification pathways were evaluated: bio-oil and bio-crude (a mixture of bio-oil and biochar), employing air and steam as gasifying agents. The Waste Reduction Algorithm was also applied to estimate Potential Environmental Impacts (PEI). Results showed that bio-oil gasification of empty fruit bunches (EFB) achieved higher energy and exergy efficiencies than rice husk (RH). For bio-crude gasification, energy efficiencies reached 50.8% and 44.3% for EFB with air and steam, respectively, while RH achieved 41.1% and 37.7%. Exergy analysis demonstrated that steam gasification improved thermodynamic performance, despite higher energy requirements. For EFB, exergy efficiencies ranged from 64.1% to 70.1% for bio-oil and from 62.9% to 71.9% for bio-crude, whereas RH presented lower efficiencies (53.9%–64.1%) due to its high ash content. Grassmann diagrams indicated that the greatest exergy destruction occurred during combustion and heat transfer, while syngas streams contributed the main exergy gains. Environmental assessment revealed maximum PEI values of 86.5 and 61.2 PEI/h for RH-derived bio-oil using air and steam. Overall, indirect gasification routes appear more efficient and environmentally favorable.