MULTICOMPONENT NON-ISOTHERMAL ADSORPTION DYNAMICS

Abstract

The present state of the theoretical basis of adsorption dynamics of multicomponent mixture with account for thermal effects accompanying adsorption is presented. Theoretical models for the non-isothermal kinetics and dynamics of adsorption in multicomponent mixtures are analyzed. A classification of these models is given, and model equations accounting for all major qualitative physicochemical features of heat and mass transfer through interfaces and in the intergranular space of porous media are presented. The following topics are considered: (1) Considerable role of thermal effects in the adsorption and desorption processes; (2) Considerable interaction of mixture components due to the non-linear nature of the adsorption isotherms of the mixture; (3) Considerable dependence of heat and mass transfer coefficients on concentration of mixture component and temperature; (4) Considerable effect of the mutual diffusion of the mixture component; (5) The role of the thermal diffusion effect (the Soret effect) and the diffusion-thermal effect (the Dufour effect) on heat and mass transfer when local concentration and temperature gradient inside the porous grains of the adsorbents are significant. The effect of slow heat and mass kinetics on the nature of distribution of concentration and temperature in the adsorber is considered. The qualitative differences between the equilibrium theory and non-equilibrium theory of multicomponent non-isothermal adsorption dynamics are shown. The coherent (steady) and incoherent (transient) patterns of concentration and thermal waves in the adsorber are analysed. The conditions of existence of the frontal patterns of mixture separation are found, and simple formulae estimating major parameters of frontal behavior in adsorption separation of mixture, which take into account of all basic qualitative features of interphase heat and mass transfer outlined in items (1) trough (5) above, are given