Demonstration of the HI decomposition section embedded with electrodialysis stack in the sulfur–iodine thermochemical cycle for hydrogen production

Demonstration of the HI decomposition section (SEC3) embedded with electrodialysis stack in the SI (sulfur–iodine) process for hydrogen production was conducted in the pressurized conditions. The goal of the experiments was to verify that the SEC3 composed of the electrodialysis (ED), distillation and HI decomposition reactor can be operated properly and show the continuous hydrogen production. The ED embedded SEC3 operation at a pressurized condition was not yet disclosed. The automated process control and commercially available engineered components were used for constructing SEC3 prior to building fully integrated skids which will be composed of the Bunsen Section (SEC1), the H2SO4 decomposition section (SEC2) and SEC3. An electrodialysis stack was installed to concentrate HI in HIx solution and overcome the H2O–HI azeotrope. A packed distillation column was used to obtain the concentrated HI gas. A Pt/SiO2 catalyst was used to decompose the HI gas. The electrodialysis stack was able to concentrate HI over azeotrope composition effectively. The H2O/HI molar ratio of the exit stream of the electrodialysis stack was approximately 4.2, which overcome the azeotropic composition of 5.2. These experiments demonstrated that hydrogen can be produced from a pressurized SEC3 of SI process, using an electrodialysis stack and engineered components. The hydrogen production rate was approximately 10 L/h at approximately 4.0 bar(g).