Reactivity Improvement of Fe-Compounds for the UT-3 Thermochemical Hydrogen Procduction Process

Abstract

The thermochemical water decomposition process is a very interesting process for hydrogen production from water using a primary thermal energy source. Solar thermal energy and nuclear thermal energy are principal candidates for the thermal energy source for this process and a carbon-free energy system can be established using these energy sources. A Ca-Fe-Br thermochemical hydrogen production process named a UT-3 cycle is the most promising one. It consists of four gas–solid reactions. Two of them are using Fe compounds and others are using Ca compounds as solid reactants. It is important to improve these solid reactants in order to industrialize this process. Low reactivity of Fe₃O₄ to FeBr₂ and sublimation of FeBr₂ were main problems. A new method using a sol–gel reaction, an alkoxide method was introduced to prepare Fe compounds instead of a conventional powder mixing method. The amount of additives and the molar ratio of the reactant to the binder material during a process of the alkoxide method were investigated to find an optimum preparing condition. Durability of the Fe-compounds in cyclic reactions was studied. A reaction analysis for the bromination reaction was also conducted.