Thermodynamical and Chemical Behavior of a Solid Hydrate during Drying

Abstract

When the solid phase of a porous medium is a hydrate, bound water is chemically linked to the anhydrous solid molecule instead of being physically adsorbed. Consequently, its elimination does not consist of a continuous desorption but of a discontinuous succession of chemical heterogeneous dehydration reactions. It results in the appearance of successive plateaus in desorption isotherm curves but also in water content and temperature-drying kinetics and profiles of a hydrate. The writing of boundary conditions between the porous medium and its surroundings explains the origin of the dehydration plateau observed in convective-drying-temperature kinetics.

Keywords:

• Convective drying
• Dehydration diagram
• Heterogeneous chemical reaction
• Porous medium
• Thermodynamic equilibrium