Performance Evaluation of a Chinese Lean Iron Ore as the Oxygen Carrier in Multi and Short-Time Redox Cycles

Abstract

The performance of a Chinese lean iron ore as the oxygen carrier in chemical looping combustion was investigated in a fixed bed reactor. Considering the short contact time between the fuel gas and oxygen carrier in the sub-pilot experimental setup, the short injection time of CO was employed in the reactor to simulate this event. The injection time of CO was set to 60 s, 50 s and 40 s respectively, to investigate its effects on the reactivity of the oxygen carrier. A total of 100 cyclic reactions under each condition were carried out to test the reactivity stability of the oxygen carrier. The oxygen carriers prior and after reactions were characterized using SEM, XRD and BET. Results showed that there was an activation process of the reactivity during initial cycles. The extension of the reaction time was beneficial to the diffusion of CO into the oxygen carrier and could improve the conversion of CO. Also, it could form larger pore volumes for gas diffusion in the oxygen carrier. However, it led to the formation of the Fe2SiO4 and severe sintering on the surface, which was harmful to the stability of the oxygen carrier’s reactivity.

Keywords

• chemical looping combustion
• lean iron ore
• reactivity
• reduction time
• CO conversion