Modeling of hydrogen isotopes separation in a metal hydride bed

A predictive model for hydrogen isotopes separation in a non-isothermal bed of unsupported palladium hydride particles is derived. It accounts for the non-linear adsorption-dissociation equilibrium, hydrodynamic dispersion, p ressure drop, mass transfer kinetics, heat of sorption and heat losses at t he bed wall. Using parameters from the literature or estimated with classic al correlations, the model gives simulated curves in agreement with previou sly published experiments without any parameter fit. The non-isothermal beh avior is shown to be responsible for drastic changes of the mass transfer r ate which is controlled by diffusion in the solid-phase lattice. For a feed at 300 K and atmospheric pressure, the endothermic hydride-to-deuteride ex change is kinetically controlled, whereas the reverse exothermic exchange i s nearly at equilibrium. Finally, a simple and efficient thermodynamic mode l for the dissociative equilibrium between a metal and a diatomic gas is pr oposed. (C) 1998 Elsevier Science Ltd. All rights reserved.