Comprehensive comparative analysis of open-loop and closed-loop iodine-sulfur thermochemical cycle for hydrogen production

The Iodine-Sulfur (IS) or called Sulfur-Iodine (SI) thermochemical water-splitting cycle is one of the most promising hydrogen production methods through heat. For future com-mercial application, the closed-loop cycle coupled to nuclear power plant and the open-loop cycle coupled to sulfuric acid plant are the best solutions. In this study, comprehen-sive comparative analysis between four different hydrogen production cases is investi-gated from the aspects of thermal efficiency calculation, economic evaluation and life cycle assessment. With reasonable assumptions, the processes of IS closed-loop and open-loop cycle are designed and optimized through the Aspen Plus software. The corresponding stream results, specific parameters of heat exchangers and reactors and power demand of the cycle are presented in detail. With sufficient internal heat exchange, the calculated thermal efficiency is 50.94% and 81.9% respectively. The levelized cost of Case A, B, C and D is 2.26, 1.82, 1.33 and 1.64 US$/kg H2 respectively with market electricity and sulfuric acid price, so Case C and D seem more competitive. With life cycle assessment (LCA) evaluation, the environmental impacts of Case A and Case D are smaller, followed by Case B and Case C. Through comprehensive consideration of the levelized cost and environmental impacts, Case B and Case D are more promising.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.