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

摘要

A two-step solar thermochemical looping reforming (STCLR) of CH4-Fe3O4 redox cycles via H2O and CO2 splitting is investigated for H-2 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 H-2 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 H-2 and CO production depends on the efficiency of methane and oxidizer (H2O and CO2) conversion. Furthermore, a substantial amount of H-2 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 H-2 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 H-2 and syngas. The results indicate that highly selective syngas with an H-2/CO ratio close to 2 can be obtained with a strong control of gamma = H2O/CO2.