Conceptual design of sulfur–iodine hydrogen production cycle of Korea Institute of Energy Research

The sulfur–iodine (S–I) thermochemical cycle offers a promising approach to the high efficiency production of hydrogen from nuclear power. S–I process was originally proposed by General Atomic. Especially, HI decomposition flowsheets of S–I process were proposed by several research groups. General Atomics (GA) studied I2 separation by extractive distillation using H3PO4. RWTH introduced the concept of reactive distillation. HIx stream coming from the Bunsen reaction is fed to the column. And HIx is distillated and decomposed at the same time to obtain hydrogen. Korea Institute of Energy Research (KIER) and Japan Atomic Energy Agency (JAEA) concentrate HIx using electrodialysis cell and concentrated HIx is fed to the column to produce HI vapor, which is decomposed to produce hydrogen. HI was separated from HIx solution by an extractive distillation using H3PO4. However, a large amount of electric energy was required to recycle H3PO4. Most of S–I processes have difficulties producing hydrogen because it has excess iodine in HI decomposition section. S–I cycle with electrodialysis cell uses membrane reactor to separate H2 and HIx. The current state of the membrane technology is not compatible with the process needs.We studied several cases of flowsheets to overcome the problems mentioned above. We revised the flowsheet by adding the iodine separator and excluded membrane reactor. We analyzed the thermal efficiency of S–I process based on revised flowsheet.