The thermodynamic evaluation and process simulation of the chemical looping steam methane reforming of mixed iron oxides

Abstract

Steam reforming chemical looping (CL-SMR) using mixed iron oxides has the potential as an alternative to the current partial oxidation (POX) and steam reforming (SMR) processes. In this study, the use of FeMoO4, Fe2ZnO4 and Fe2MnO4 as oxygen carriers (OC) under the CL-SMR reaction scheme was proposed to overcome the current disadvantages of methane POX and SMR processes. This research is aimed at finding potential iron-based metal oxides for the production of syngas, which can be regenerated under favorable conditions in steam, while producing H2. Thermodynamic evaluation and process simulation of the CL-SMR reaction scheme using mixed iron-oxides was performed. Results indicate that FeMoO4, Fe2ZnO4 and Fe2MnO4 generated syngas at 750 °C, 730 °C and 600 °C, respectively. However, FeMoO4 was not fully regenerated under favorable conditions, whereas Fe2ZnO4 and Fe2MnO4 were completely regenerated at 440 °C and 640 °C, respectively. Fe2MnO4 showed the most favorable operating conditions among the studied OC towards the production of syngas. Preliminary experimental studies involved the synthesis of Fe2MnO4 through a solid-state method using Fe2O3 and MnO as precursors, which was characterized via XRD, while its redox performance was evaluated in a TGA CH4–H2O redox cycle, with reduction using CH4 followed by the steam oxidation of OC. Results indicate that both reduction with methane and oxidation with water vapor using Fe2MnO4 present reasonable reduction–oxidation rates to be used in the CL-SMR reaction scheme, verifying the feasibility of the theoretical study performed in the present investigation.