Performance Evaluation and Kinetic Analysis of an Iron Ore as Oxygen Carrier in Chemical Looping Combustion

Chemical looping combustion (CLC) provides an inherently cost-effective method for carbon capture by employing a solid oxygen carrier (OC) to transfer lattice oxygen from air to fuel. The search for low-cost, high-performance natural OCs is crucial for the large-scale deployment of this technology. A natural iron ore containing 41.34% Fe2O3 was systematically evaluated as OC for the CLC of CO. Its redox performance was quantified in a fixed-bed reactor between 750 °C and 900 °C with CO concentrations of 10–20%. Multi-cycle tests were conducted to assess stability. Kinetic analysis of the initial cycles was performed using an integral model fitting method. Multi-cycle tests revealed that the fresh ore achieved peak conversions of 48.9% at 750 °C and 77.2% at 900 °C. However, severe sintering occurred beyond 850 °C after the first cycle, causing approximately a 50% drop in OC conversion. Interestingly, once sintered, a self-activation phenomenon was observed during subsequent cycles; the OC conversion slowly recovered from 32% to 37% from the second to the fifteenth cycle under the aggressive conditions (900 °C, 20% CO). Kinetic analysis of the initial cycles (before sintering) revealed low apparent activation energies, ranging from 15.93 to 19.13 kJ mol−1, which are significantly lower than the typical literature values for iron-based ores. This work underscores the potential of natural iron ores as economical and sustainable OCs for CO-rich fuels. The observed self-activation ability of the sintered OC is a promising finding for long-term operation. The results also highlight the critical importance of operating conditions to avoid deep reduction and sintering, necessitating a high solids inventory and a moderate oxygen-to-fuel ratio in practical CLC systems.