EFFECTS OF NONIDEAL ADSORPTION EQUILIBRIA OF GAS-MIXTURES ON COLUMN DYNAMICS

A theoretical study has been made for simulating the dynamic behavior of non-ideal gas mixtures in an isothermal fixed-bed adsorber. A mathe matical model was developed which takes into account the non-ideality of adsorbable species on the adsorbed phase under equilibrium. The mod el is based on both the real adsorbed solution theory (RAST), which in corporates the activity coefficients in the multicomponent isotherm eq uations to account for the deviations from ideality, and the linear dr iving force (LDF) model for representing diffusion resistance inside t he adsorbent particles. To describe the effect of non-ideal adsorption equilibrium of gas mixtures on the breakthrough curves, we considered several model mixtures of binary and ternary components which exhibit non-ideal behavior with azeotropic crossovers in the composition doma ins at equilibrium. Sample calculations of a fixed-bed adsorption were done with various inlet gas compositions of binary and ternary mixtur es, respectively, at a fixed total concentration. From the calculation results, it was shown that the order of breakthrough curves could be changed at a certain value of inlet gas composition ratio. This result implies that the dynamic behaviors of fixed-bed adsorption are greatl y influenced by multicomponent equilibrium models. Furthermore, the re versal phenomenon of breakthrough curves could not be simulated by the ideal adsorbed solution theory (IAST).