Kinetics of the Solid-State Thermal Dehydration of Sodium Acetate Trihydrate: Effects of Water Vapor Pressure and Particle Size

The universal kinetic description of the reversible thermal dehydration of sodium acetate trihydrate (SA-TH) across a range of temperature and water vapor pressure ( p (H 2 O)) was demonstrated toward its application to the thermochemical energy storage system. The thermal dehydration of SA-TH in the solid state can be observed within a limited range of temperatures and atmospheric water vapor pressures ( p (H 2 O) ATM ), due to the occurrence of efflorescence at ambient temperature in a dry atmosphere and melting at a temperature 30 K above room temperature. A systematic tracing of the thermal dehydration process at various p (H 2 O) ATM values was accomplished by employing a humidity-controlled thermogravimetry system. The reactions in flowing wet N 2 with various controlled p (H 2 O) ATM values were subjected to the universal kinetic description across varying temperatures and p (H 2 O) ATM values by extending kinetic equation and computation method. This extension entailed the incorporation of an accommodation function for the effect of p (H 2 O) ATM and the consideration of the effect of self-generated water vapor in a stepwise manner. This approach facilitated a comparison of the universal kinetic behaviors of the thermal dehydration of the SA-TH samples with different particle sizes based on a physico-geometrical consecutive reaction model. The demonstrated universal kinetic analysis is proposed as a practically useful method for characterizing the reversible thermal dehydration of inorganic hydrates and a potential tool to obtain further insight into the physicochemical and physico-geometrical kinetic features of the reversible heterogeneous processes in solid–gas systems.