This work is concerned with customization of the existing electrolyte thermodynamic model for process simulation and experimental studies on the sulfuric acid decomposition process of the SI cycle, using a commercial steady state simulator. An electrolyte thermodynamic model for the sulfuric acid water system was tailored with four candidates available in commercial software, utilizing data from Perry's Handbook. Simulation of the sulfuric acid decomposition process comprising a flash separator, distillation column and decomposer was validated with the experimental results. To facilitate the lumped-parameter steady-state model-based simulation of sulfuric acid decomposition, the decomposer was conceptually decoupled into three sections: evaporation, H2SO4 dissociation, and SO3 catalytic reduction to SO2. The process simulation results exhibited good agreement with experimental data. This work contributes to future work on simulation and experimental study of a scaled-up process system and exergy analysis for an optimal energy-efficient sulfuric acid decomposition process in the SI cycle. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.