Mechanism-based kinetic modeling of magnesium sulfate hydration for thermochemical energy storage

Magnesium sulfate and water form a promising reaction pair for thermochemical energy storage due to their high energy density, yet practical implementation is hindered by slow hydration kinetics. Although various studies have reported qualitative observations of this behavior, a quantitative assessment of how key operating conditions affect the reaction rate has been lacking. This study systematically examines the influence of temperature, water vapor pressure, particle size, and layer thickness on the hydration rate of magnesium sulfate using thermogravimetric analysis. A kinetic model is developed to quantify the dependence of the reaction rate on these parameters. The results show that the hydration proceeds through a single-step reaction that is well described by a contracting-sphere model. Model simulations closely reproduce the experimental data, enabling reliable prediction of hydration behavior under realistic operating conditions. The findings clarify the underlying reaction behavior and provide a foundation for reliable performance prediction in future reactor design and system modeling.