A novel biomass gasification process for the generation of inherently separated syngas using the concept of chemical looping technology

Abstract

Biomass-based hydrogen generation has been showing a potential prospect in solving the global environment and energy challenges. This study introduces a novel chemical looping system, known as chemical looping partial oxidation and hydrogen generation (CLPH) process, which can generate inherently separated syngas from biomass, thus presenting a good application prospect. The feasibility of this system and the selection of appropriate oxygen carriers (OCs), which were the key to the success of this system, were investigated in this work. Four MFe₂O₄ (M=Ni, Co, Ca, Ba) OCs were chosen according to the modified Ellingham diagram, and their performances as well as the reaction pathway of BaFe₂O₄ and C were comprehensively investigated. The results show that all OCs exhibit a good solid-solid reactivity, but the CO selectivity of CaFe₂O₄ and BaFe₂O₄ (around 60%) are higher than that of CoFe₂O₄ and NiFe₂O₄ (around 20%). Additionally, the cycle performance of CaFe₂O₄ is worse than that of BaFe₂O₄, which is owing to the poor self-healing property. Thus, BaFe₂O₄ was chosen as the ideal OC for the CLPH process. A successful biomass gasification process for the generation of inherently separated syngas was developed, achieving a carbon conversion rate of 93%, CO selectivity of ≥ 60%, wonderful hydrogen yield of ≥ 1700 mL/g·biomass char and hydrogen purity of ≥ 94% over 5 cycles.