The kinetics and mechanism of lignite dehydration

The dehydration of a homogeneous cubic sample of ‘woody’ lignite at ca. 290 K follows a modified contracting cube equation, dp/dt=k(1 –α)2/3(1 –β), in which k is a constant, α is the fraction of the sample dehydrated and β is the ratio of the vapour pressure of water at time t compared to its saturated value. The rate depends on the competitive evaporation and condensation of water via the dehydration interface. The system provides a satisfactory kinetic model for the rate of release of non-bonded water across a solid/gas interface.