Hydrogen-rich syngas production with tar elimination via biomass chemical looping gasification (BCLG) using BaFe2O4/Al2O3 as oxygen carrier

Biomass chemical looping gasification (BCLG) is a promising technology for biomass utilization. The selection of appropriate oxygen carrier (OC) is one of the key issues in BCLG process. In this work, 30% Al2O3/BaFe2O4 (30ABF) synthesized via the direct decomposition method coupled with mixed calcination process was applied as OC in BCLG for hydrogen-rich syngas production. 30% Al2O3/Fe2O3 (30AF) was prepared by incipient wet impregnation method for comparison. Gasification experiments were conducted in a fixed bed reactor. The effects of OC-biomass mixing method, ratio of OC and biomass (O/B), temperature and steam feeding rate on the performance of BCLG were investigated. The results indicated that 30ABF exhibited a high reactivity with char but a low reactivity with syngas. The hydrogen-enriched syngas was obtained when O/B was 0.6 and steam volume fraction of 33.6% at 850 degrees C. The properties of the fresh and used OCs were characterized using different methods including XRD, SEM, BET and XPS. To deeply understand the reaction mechanism, adsorption of C atom over BaFe2O4 surface was analyzed by the method of density function theory (DFT). It was found that the energy barriers of CO* forming and dissociation were 0.252 eV and 0.165 eV, respectively. Thus the forming of CO* is the main rate determining step. The thermodynamic calculation results indicates that Delta G(T, p) of total system at 900 degrees C was -2.621 eV.