The Japan Atomic Energy Agency (JAEA) has been conducting R&D on hydrogen production by the thermochemical Iodine-Sulfur (IS) process to meet the massive hydrogen demand in the future hydrogen economy. In the IS process, sulfuric acid (H2SO4) is evaporated and decomposed into H2O and SO3 in a H2SO4 decomposer operated under high-temperature condition up to 500°C. We have proposed a new decomposer concept of a block-type heat exchanger made of SiC ceramic, which has a salient corrosion-resistant performance under severe corrosion condition. To verify the mechanical feasibility of the concept, the temperature distributions of sulfuric acid and helium gas were analyzed using a newly coded analytical system applicable to binary mixtures such as H2SO4 whose boiling point depends on the concentration. Thermomechanical simulations with a general-purpose FEM code, which used the heat exchange simulation results, showed that the maximum stress was generated around the dryout region, which was about half of the allowable tensile stress of SiC.
