Hydrogen production by SI process, with electrodialysis stack embedded in HI decomposition section

• Hydrogen is produced by the SEC3 of sulfur–iodine (SI) process under pressurized conditions.
• An electrodialysis stack is embedded in HI decomposition section to concentrate HI.
• Increasing the distillation column pressure increases the H2O/HI ratio.
• Increasing the inlet I2 ratio decreases the H2O/HI ratio in the raffinate.
• 18.3–50 L/h H2 is produced based on operating conditions and HIx feed composition.

Hydrogen production by the sulfur–iodine (SI) process, with an electrodialysis (ED) stack embedded in the HI decomposition section (SEC3) to concentrate HI in the HIx solution and overcome the pseudo-azeotrope, was conducted under pressurized conditions. The HIx solution of H2O/HI = 5.63–6.13 and I2/HI = 0.57–1.97 was supplied to the SEC3. HI gas was concentrated in a packed distillation column and decomposed over Pt/Al2O3. The experimental results of distillation column operation under different feed rates and HIx compositions are reported. The raffinate from the column showed a pseudo-azeotropic HIx mixture, as predicted in previous research. The dynamic responses of the ED stack were examined during the start-up period according to the HIx feed composition at the anode inlet. The ED voltage changed with the I2 concentration in the inlet flow. The proton transport number (t+) and electro-osmosis coefficient (β) were estimated for the ED stack during the operations. Hydrogen production ranged from 18.3 to 50 L/h, depending on the operating conditions and HIx feed composition.