Contemporary scenarios for future energy supply include using enormous amounts of hydrogen as an energy carrier for fuel cells and as a reagent for upgrading heavy oils and converting coal to liquid fuels. The Sulfur-Iodine cycle is a closed-cycle, all fluid-phase process to thermochemically decompose water into hydrogen and oxygen that may be the most energy efficient among the many proposed. Current process simulation studies suggest that the energy requirements are unacceptably high, especially in the section where H₂ is formed from HI and separated from the recycled I₂ by reactive distillation. The reliability of these analyses, and the testing of creative alternatives, is hampered by the lack of reliable data to build the complicated properties models for these systems.

To make an informed decision with regard to the ultimate feasibility of the S-I process, accurate predictions of phase and reaction equilibria are essential to yield reliable process simulations for equipment and energy requirements. A new properties model, described elsewhere, has been utilized to find optimal configurations and conditions for this section of the S-I process. Significantly different results are found compared to the literature; these suggest that alternative arrangements could lead to improved efficiencies for the process. This paper will describe our methodology and current findings about the RD column, as well as indicate potential opportunities in processing for improved efficiency.