A systematic modelling approach for reaching low oxygen partial pressures with hybrid thermochemical oxygen pumping

Thermochemical oxygen pumping (TCOP) uses reversible redox reactions to remove oxygen at low partial pressures, with heat providing the primary driving force for the thermochemical stage. A redox-active material releases oxygen during high-temperature reduction and reabsorbs it during low-temperature oxidation at substantially lower oxygen partial pressures, thereby transporting oxygen from a low- to a high-pressure environment. Depending on the pumping material and heat recovery, hybrid TCOP can reduce the energy demand relative to standalone mechanical vacuum pumping in the low-pressure regime. This work combines optimization of the thermochemical operating conditions, mechanical vacuum-pump coupling, and sensible-heat recovery with separate estimates of connecting-pipe transport and supporting-pump requirements. The energetically favorable operating parameters , , and are determined for cobalt oxide and Mn- and Fe-based perovskites as functions of inlet oxygen partial pressure and heat recovery factor (HRF), using numerical optimization strategies adapted to the respective analyses. For the detailed Ca_0.8Sr_0.2MnO₃ (CSMO20) operating maps, the calculated specific hybrid energy demand ranges from approximately 288 to 2432 kJ mol_O2^-1. At 1 Pa and 60% sensible-heat recuperation, CSMO20 requires approximately 1245 kJ mol_O2^-1. The investigated Ca_1-xSr_xMnO₃ materials show similar performance: CaMnO₃ is most efficient at low heat recovery factors, whereas Ca_0.8Sr_0.2MnO₃ becomes slightly more favorable at higher values. SrFeO₃ outperforms these materials over the full range because of its lower sensible heat demand. Co₃O₄ exhibits the highest efficiency up to HRF ≈ 0.8, where its large oxygen exchange capacity compensates for its energetic penalty; at higher heat recovery factors, the perovskites become more favorable owing to lower oxygen affinity and reduced thermodynamic penalty for oxygen release. Practical cobalt oxide use remains challenged by toxicity concerns and limited cycling stability. Flow-limited transport times through pipes are further estimated, and the effective pumping speed of the companion vacuum pump is inferred from cycle-time constraints. The resulting design maps and operating windows provide actionable guidance for TCOP-based pressure reduction.