Insight into the Fe₂O₃/CaO-based chemical looping process for biomass conversion

In this study, the looping materials of Fe₂O₃, CaO, mechanically mixed CaO and Fe₂O₃, and chemically synthesized Ca₂Fe₂O₅ were tested for comparison of the performance and gas evolution processes. The reaction mechanism was illustrated to have an insight into the Fe₂O₃/CaO-based chemical looping process. Results found that the reduction from Fe₂O₃ to Fe₃O₄ trended to form CO₂ while the transition of Fe₃O₄ to Fe happened after 650 °C was most likely to release CO. CO₂ adsorption by CaO during 400-600 °C and further desorbed at higher temperature for CO₂ Boudouard reaction which enhanced the biomass conversion. Mechanically mixed CaO and Fe₂O₃ maintained the properties of CaO and Fe₂O₃ with CO₂ transfer and oxygen releasing during chemical looping reaction process, while the synthesized Ca₂Fe₂O₅ presented hard reducibility which prefer to generate CO with the highest concentration (34.96 vol%) during chemical looping process at 850 °C.