Study on the redox characteristics of CaCo based oxygen carrier for Chemical Looping Combustion

We investigated whether a CaCo-based oxygen carrier could be an oxygen-transfer particle for Chemical Looping Combustion (CLC). The analysis was carried out using TGA to see the redox characteristics of the cycle. 15% H-2/N-2 was used as the reducing gas, and air was used as the oxidizing gas. The CaCo-based oxygen carrier maintained a high oxygen-transfer capacity of about 16 wt% for 10 cycles. Also, the oxygen-transfer rate was relatively stable over 10 cycles. The maximum oxygen-transfer rate was about 0.022 mmol O-2/g/s in the reduction section. The maximum oxygen-transfer rate in the oxidation section was about 0.022 mmol O-2/g/s. From the XRD results, the CaCo-based oxygen carrier exhibited a similar XRD pattern after the 10th-cycle oxidation, which confirmed that the phase was stably recovered even though the CaCo-based oxygen carrier was completely reduced to CaO and Co metal during reduction. Although some agglomeration was observed, it did not affect overall oxygen transfer capacity and rates. Conclusively, CaCo-based oxygen carriers show high performance and phase stability, and thus can be potential candidates for oxygen carriers in CLC process.