A systematic methodology for the evaluation of alternative thermochemical cycles for hydrogen production

Here we present and demonstrate a process systems engineering-based methodology for the initial evaluation of thermochemical cycles for hydrogen production. The five major components of the proposed strategy are (i) conceptualization, (ii) reaction cluster synthesis, (iii) flowsheet design, simulation, and analysis, (iv) process integration and (v) performance evaluation. The resulting approach involves selecting atomic and molecular species with desired properties, identifying suitable thermodynamically feasible cycles of reactions based on these species, screening and sequencing the most promising of the identified reaction clusters, designing a process of unit operations to carry out the reaction cluster, and integrating those processes to maximize thermodynamic efficiency and resource utilization. An integrated suite of resources, including AspenOne software, is employed to aid in implementation of the algorithm. The strength of the proposed methodology is demonstrated through an illustrative example involving the commonly studied Fe-Cl system. The results of our systematic evaluation provide cycles with estimated base efficiencies ranging from 35% to 49%.