Numerical simulation of a PSA system using a pore diffusion model

Abstract A mathematical model has been developed for a pressure swing adsorption (PSA) system (heatless drier) in which the controlling resistance to mass transfer is diffusion within the pores of the adsorbent particles. The model equations are solved numerically by the method of orthogonal collocation. By comparing the solutions from this model with the solutions derived from the simpler linear driving force model it is shown that the simpler model provides an acceptable approximation provided that the coefficient [Ω in eq. (1)] is chosen correctly. The appropriate value of Ω depends on the cycle time and to a lesser extent on the degree of isotherm non-linearity and the nature of the diffusion mechanism, varying from about 40 at low cycle times to 15 or even lower at large cycle times. However, over a fairly wide range of conditions typical of PSA operation the linear driving force model with Ω = 40 provides an acceptable approximation, except in the initial region of the transient. The value of Ω recommended by Glueckauf for modelling of a fixed bed (Ω = 15) is approached only at rather large cycle times and is clearly inappropriate for a PSA system under most practical conditions.