Detailed kinetic modeling of homogeneous HI decomposition for hydrogen production—Part II: Effect of I2 on HI decomposition

The kinetic modeling of homogeneous decomposition of hydrogen iodide (HI) and HI/H2O vapors with the addition of diatomic iodine (I2) using the mechanism proposed in the companion work (part I) in the sulfur–iodine cycle was investigated in this paper. Thermodynamic results calculated by FactSage and the kinetic experiment verified the applicability of the mechanism. The effect of temperature, residence time, pressure, HI/H2O/I2 molar ratio, HI/I2 molar ratio, and sensitivity analysis on the HI conversion was observed in the modeling process. The addition of small amount of diatomic iodine greatly decreases the HI conversion, and the overall pressure could promote the HI decomposition rate in the kinetic process. Sensitivity analysis shows that hydrogen yield was most sensitive to reactions (4) HI + H = H2 + I, (1) HI + HI = H2 + I2, (5) HI + I = I2 + H, and (8) HI + OH = H2O + I. The existence of diatomic iodine increases the reverse reaction of (1) and (5).