Production mechanism analysis of H2 and CO via solar thermochemical cycles based on iron oxide (Fe3O4) at high temperature

Abstract

In this paper, the production mechanism analysis of H2 and CO based on iron oxide was investigated. To deeply understand the reaction mechanism of the inner working of chemistry models, detailed chemical reaction mechanisms describing H2 and CO formation were conceptually structured in a hierarchical manner with the assistance of reaction paths diagram. However, the main reaction pathways leading to syngas (H2 and CO) formation derived from the conversion of H2O, CO2 and Fe(A). The study revealed that the reactivity of H, O, HO and HO2 in the reaction medium was crucial to determine syngas yield. The species reactivity in gas-Fe(A) reaction was limited by the rates of lattice oxygen extraction and diffusion from gas species to the iron bulk surface to replenish the extracted oxygen. However, the reaction paths diagram showed the main Fe(A) bulk phase of iron was not completely transformed to the fully oxidized Fe3O4 phase because of the restricted oxygen transfer to Fe(A) possibly. The model has indicated a better control of surface temperature and operating pressure could result in high reactivity of species in the reaction medium. Moreover, the combination analysis of Fe3O4 phase transformations and produced gas led to describe syngas production over several cycles of iron oxide redox reaction.