Start-up dynamic behaviors of a HI–I2–H2O distillation column for the sulfur-iodine hydrogen production cycle

• Introduction of a HIx distillation column for the SI hydrogen production process.
• Start-up simulation of the HIx distillation column using KAERI-DySCo.
• Discovery of “HI overshoot” as one of start-up phenomena.
• Design and operation information of the HIx distillation column.

The sulfur-iodine (SI) cycle to produce hydrogen from water requires a HIx multistage distillation column to obtain hyperazeotropic hydriodic acid vapor as a top product that can be afterward decomposed into hydrogen and iodine. To design a HIx multistage distillation column that can be applied to the cycle, its static and dynamic simulation is essentially demanded. A 50NL-H2/h scale SI test facility to be operated under a pressurized environment has been constructed in Korea. This study focuses on the HIx multistage distillation column (HIxMDC-50L) for the 50NL-H2/h SI test facility. The HIxMDC-50L was designed and installed in 2013. Based on the design specifications and operation method, the start-up behavior of the HIxMDC-50L has been analyzed using the simulation code “KAERI-DySCo”. As a result of the start-up dynamic simulation, it is confirmed that the HIxMDC-50L will advance to the steady state value within 1050 s to fulfill a hydrogen production rate of 50NL-H2/h. On the other hand, not only the effects of the column design parameters on the progress to a steady state but also the effects of several operation variables on the top product have been evaluated for safely operating the HIxMDC-50L.