Experimental study on the purification of HIx phase in the iodine–sulfur thermochemical hydrogen production process

Purification of hydriodic phase (HIx) plays an important role in avoiding the undesirable side reactions between HI and H2SO4 in the sulfur–iodine thermochemical cycle. In this paper, a series of experiments on HIx phase purification were conducted by means of a stirred reactor using N2 as stripping gas. The effects of the iodine concentration, reaction temperature, and the striping gas flow rate on HIx phase purification were investigated systematically in terms of the conversion of H2SO4 and the reaction types during purification. It was observed that the iodine concentration played a significant role in dictating the reactions during purification. The quantitative analysis of the compositions of the initial and purified HIx phases showed that not only the conversion of H2SO4 was enhanced but also the side reactions were effectively impeded by increasing the iodine concentration, temperature and the stripping gas flow rate. Based on the experimental data, the suitable operating conditions for HIx phase purification were proposed.

► Effects of I2 content, temperature and N2 flow rate on purifying HIx were studied.
► The suitable operation conditions for HIx phase purification were proposed.
► The reverse Bunsen reaction predominated at the mole ratio I2/HI of 1.5.
► Purifying at elevated temperature favored the reverse Bunsen reaction.
► Increasing N2 flow rate accelerated the reaction rate of the reverse Bunsen.