Kinetics of oxygen release from iron-rich sludge ash synergized with perovskite oxygen carriers

In chemical looping treatment of high-ash sludge, contact and flow between sludge ash and oxygen carriers are inevitable. Whether sludge ash rich in active components such as Fe₂O₃ exhibits synergistic oxygen-carrying capacity and promotes phase stabilization of iron-based oxygen carriers warrants investigation. Thermogravimetric analysis (TGA) was conducted on an industrially prepared CaMn_0.5Fe_0.5O_3−δ perovskite oxygen carrier (POC), iron-rich sludge ash (SA), and their equimass mixture (50POC/50SA). The isothermal reaction kinetics of oxygen release from the three oxygen carriers were studied under a 5% H₂ atmosphere. The results indicate that the presence of SA delays the oxygen decoupling process of POC to a certain extent. The mass loss during oxygen release is slightly greater than the theoretically weighted value, and this difference gradually diminishes with increasing temperature. The apparent activation energy (E_a) of oxygen release for the mixed sample is 46.135 kJ/mol, which is 1.973 kJ/mol lower than the theoretically weighted value. This indicates a positive synergistic effect between SA and POC, enhancing the oxygen-carrying capacity and reactivity of the perovskite oxygen carrier. Consequently, iron-rich SA plays a significant oxygen-carrying role in the chemical looping conversion of sludge.