Ca2Fe2O5 (C2F) has been recently considered as Oxygen Carrier (OC) for fuel-assisted Chemical Looping Water Splitting (CLWS), due to its high redox stability and low equilibrium pO2. This study delves into the stability of C2F in CLWS at varying pressures, since operating at high pressure eliminates the need for energy-intensive compression steps in syngas-based GTL processes and in hydrogen production and transport. Stability of C2F was tested in a custom-built termogravimetric analyser, subjecting samples to 50 H2-H2O cycles at pressures ranging from 1 to 20 bar. Hydrogen served as a surrogate fuel to avoid complications related to carbon deposition. Tested samples has been characterized by XRD and SEM. Experimental results revealed reversible reduction kinetics decline over cycles at non-ambient pressures. However, full reactivity restoration was achievable through a prolonged air oxidation step. Implementing alternating H2-H2O and H2-air cycles ensured stable performance. Kinetic models were developed for H2 reduction (temperature: 750-900 °C, pressure: 1-20 bar, H2 molar fraction: 0.2-0.6) and H2O oxidation (temperature: 650-700 °C, pressure: 1-10 bar, H2O molar fraction: 0.2). Analytical techniques such as SEM-EDS and XRD supported the choice of reaction models. Overall, the study contributes to identifying effective process strategies for high-pressure CLWS operation, emphasizing the importance of pressure in enhancing the efficiency and versatility of the process.
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