Experimental investigation of La0.6Sr0.4FeO3 -δ pellets as oxygen carriers for chemical-looping applications

Abstract

Lanthanum Strontium Ferrite (LSF), as an oxygen carrier, is used for chemical looping H₂ production and CO₂ utilization. In this work, the first attempt to upscale and understand the heat and mass transfer using 400 g of LSF pellets in a dynamically operated packed bed reactor is carried out.

Experiments were conducted at 650–820 °C and 1–5 bar_g, evaluating the pellets' reactor heat management, phase stability, and mechanical integrity over 70 h for the high-temperature redox cycling in chemical looping water-gas shift (CL-WGS) and chemical looping reverse water-gas shift (CL-RWGS) reactions.

Key results at the reactor scale indicate a maximum cyclic average H₂O-to-H₂ conversion of 31%, with a peak oxygen carrier capacity for CL-WGS of 0.38 mmol/g_LSF. In the case of CL-RWGS, a peak CO₂-to-CO conversion of 99.8% was achieved, with an oxygen carrier capacity of 0.57 mmol/g_LSF.

Reactor heat management for exothermic and endothermic redox reactions showed the ability to maintain a high temperature profile where the heat front lagged the reaction front over a 15 cm reactive bed length. A maximum ΔT of 45 °C and 35 °C were observed during the oxidation of the LSF bed with H₂O and CO₂, respectively. In the case of air oxidation, a maximum ΔT of 120 °C indicates that the reaction is more exothermic and can be used to raise the temperature of the bed especially if heat is required to sustain the process.

No evidence of material performance degradation was recorded over 70 h of testing, maintaining the pellets' operational cyclability, phase stability, and mechanical integrity. The results demonstrate the robustness of the material, and they are encouraging versus the scalability of LSF for chemical looping applications, into H₂ production and CO₂ utilization processes.