MATHEMATICAL-MODELING OF THE ADSORPTIVE SEPARATION OF MULTICOMPONENT GASEOUS-MIXTURES

A general dynamic model describing the adsorptive separation of multic omponent gaseous mixtures is developed in this study. The dusty-gas mo del and D'Arcy's law are used to describe the diffusive and viscous ma ss transport in the adsorbing bed, respectively, and the local equilib rium assumption or the linear driving force approximation are used for the uptake rate. The versatility of the developed model is demonstrat ed by applying it to separation of binary, ternary and quaternary mixt ures by pressure swing adsorption (PSA). The relative importance of th e diffusive (bulk and Knudsen) and viscous mass transport and the effe cts of the different uptake rate representations are also investigated . For the PSA process, it is found that viscous transport dominates in the adsorbing bed and the inclusion of other modes of transport in th e model equations has practically no effect on the solution. However, for dynamic processes occurring in porous media of smaller pore sizes (macroporous membranes, for instance) both the viscous and the diffusi ve modes of transport must be included in the overall model to predict the system behavior correctly. The model with only viscous transport in bed and the linear driving force approximation for the uptake rate is the recommended option for modeling PSA operations, provided that t he LDF approximation is applicable, since it is easier to handle numer ically and reduces to the equilibrium model in the limiting case of la rge adsorption rate constants. Copyright (C) 1996 Elsevier Science Ltd