Analysis of Two‐Step Solar Thermochemical Looping Reforming of Fe3O4 Redox Cycles for Synthesis Gas Production

A two‐step solar thermochemical looping reforming (STCLR) of CH4—Fe3O4 redox cycles via H2O and CO2 splitting is investigated for H2 and CO production. The P1 approximation is adopted for the radiation heat transfer and high‐temperature thermal characteristics of active materials in the reaction medium. A benchmark experimental setup for the conversion of solar energy to syngas based on the solar thermochemical technology is presented. The effects of operating conditions on the yield of H2 and CO as well as syngas production are investigated at both thermal reduction and oxidation steps. It is found that the key performance of two‐step CH4—Fe3O4 redox cycles for a higher H2 and CO production depends on the efficiency of methane and oxidizer (H2O and CO2) conversion. Furthermore, a substantial amount of H2 and CO production with carbon deposition is obtained when the thermal reduction is extended to the mixed oxide solid solution (FeO—Fe). Among the oxygen carriers, FeO exhibits a higher oxygen exchange for H2 production. However, the synergetic effect of FeO—Fe reactivity strongly contributes to syngas yield. The present solar reactor model can significantly contribute to the reduction of greenhouse gas emission by utilizing 40% of CO2 emissions into solar fuels such as H2 and syngas. The results indicate that highly selective syngas with an H2/CO ratio close to 2 can be obtained with a strong control of γ = H2O/CO2.