Effects of the operation modes on the HIx phase purification in the iodine-sulfur thermochemical cycle for hydrogen production

In the iodine-sulfur thermochemical water-splitting process for hydrogen production, purification of hydriodic phase (HIx) had to be adopted to eliminate the minor components in the HIx phases (the mixture of mainly HI, H2O, I2 and small amounts of H2SO4), so as to avoid the undesirable side reactions between HI and H2SO4. In this work, experimental studies on HIx phase purification were carried out. Effects of the operation modes (such as batch operation, continuous operation and the mixed modes of the continuous and discontinuous operation), and process parameters (such as the reaction temperature, feed flowrate of the HIx solution, and the flowrate of the stripping gas N2) on the purification of HIx phase were investigated. The experimental results showed that increase of temperature and N2 flowrate, and decrease of feed flowrate of HIx solution favored the removal of H2SO4 from HIx phase. The purification efficiency would be improved by combining the continuous operation with the batch operation during the purification process. These results were favorable for achieving the closed operation of IS cycle.