Experimental Study of the Characteristics of HI Distillation in the Thermochemical Iodine–Sulfur Cycle for Hydrogen Production

Hydrogen energy, as a clean, renewable, and high-calorific energy carrier, has garnered significant attention globally. Among various hydrogen production methods, the thermochemical iodine–sulfur (I-S) cycle is considered the most promising due to its high efficiency and adaptability for large-scale industrial applications. This study focuses on the distillation characteristics of the HIx (HI–I2–H2O) solution within the I-S cycle, which is crucial for achieving the high-concentration HI necessary for efficient hydrogen production. Previous methods, including phosphoric acid extraction–distillation and reactive distillation, have addressed azeotrope issues but introduced complexities and equipment demands. This research constructs a hypo-azeotropic HIx solution distillation experimental system and uses the Aspen Plus v14 software to optimize distillation parameters. By analyzing the effects of feed stage, reflux ratio, and feed temperature, the study provides essential data for improving distillation efficiency and supports the scale-up of I-S cycle technology. The findings indicate that optimal distillation is achieved with a feed position at 1/3 column height, a reflux ratio of 1.4, and a feed temperature near the boiling point, enhancing the feasibility of industrial hydrogen production via the I-S cycle.