Analysis of internal heat exchange network and hydrogen production efficiency of iodine-sulfur cycle for nuclear hydrogen production

Nuclear energy enables large-scale carbon-free hydrogen production, and the coupling of the very-high-temperature gas-cooled reactor and iodine-sulfur (IS) cycle has the potential to achieve efficient hydrogen production. This study develops the flowsheet of IS process, performs process simulation, designs the internal heat exchange network using pinch point technology, and discusses the thermal efficiency of hydrogen production in detail. The results show that if all heat released by heat exchangers in H2SO4 and HI sections can be fully recovered and utilized, the upper bound of the thermal efficiency of the IS process is 51.9%. The pinch point temperature difference has little impact on the performance of the heat exchange network of the H2SO4 section, but greatly influences the performance of the heat exchange network of the HI section. When the pinch point temperature difference is 5 degrees C to 20 degrees C, the input heat duties required by the H2SO4 and HI sections are reduced by 23.9% to 25.0% and 20.8% to 50.8%, respectively, compared with those without heat exchange networks. After designing the heat exchange network, considering the recovery and utilization of a portion of waste heat, a more realistic hydrogen production efficiency of 30.0% to 37.1% corresponding to the pinch point temperature difference of 5 degrees C to 20 degrees C is given. Highlights Process simulation of IS cycle is conducted to analyze its energy consumption. Internal heat exchange network is designed using pinch point technology. Network performance is studied at different pinch point temperature differences. Thermal efficiency of hydrogen production is discussed in detail.