Detailed kinetic modeling of homogeneous HI decomposition for hydrogen production, part I: Effect of H2O on HI decomposition

A new, detailed kinetic model was developed for the homogeneous decomposition of HI–H2O solutions in vapor phase in the sulfur–iodine cycle. The kinetics of the process was represented by a reaction mechanism involving 32 reactions and 11 species. Comparisons between the kinetic calculations and experimental data showed that this model correctly predicted the hydrogen yield at the 500 °C–1000 °C temperature range under 1 atm. The effects of temperature, reaction time, and HI/H2O ratio on HI decomposition and hydrogen sensitivity analysis were investigated in the modeling process. The model predicted that the effect of the addition of H2O changed from inhibiting the decomposition ratio to promoting it with increasing temperature. The sensitivity analysis showed that elementary reactions (1) HI + HI = H2+I2, (4) HI + H = H2 + I, (5) HI + I = H + I2, and (8) HI + OH = H2O + I played important roles in hydrogen production. The reaction path of HI decomposition with H2O was constructed based on detailed kinetic modeling and sensitivity analysis results.

► Experimental results were used to validate the mechanism.
► H2O changed from inhibiting HI–H2O decomposition to promoting it at 850 °C.
► Sensitive analysis was conducted to elucidate the important reaction pathways.
► The reaction path of HI decomposition with H2O was constructed.