Pinched wave design of a four-zone simulated moving bed for linear adsorption systems with significant mass-transfer effects

Abstract

For linear adsorption simulated moving bed (SMB) systems, a pinched wave design (PWD) method was developed to maintain desired yield and purity against the possible fluctuations in operating and system parameters. The operating parameters under consideration include pump outputs and step time. The system parameters under consideration include bed voidage, isotherm constant, extra-column dead volume, intraparticle diffusivity, and axial dispersion coefficient. Because bed voidage has a different effect on the linear velocity of a key concentration wave depending on the magnitude of isotherm constant, the effect of bed voidage deviation was coupled with that of isotherm constant deviation in the developed PWD equations. Detailed rate-model simulations were used to validate the PWD for linear adsorption systems. The results showed that the developed PWD was successful in providing an exact margin to guarantee high yield and high purity against the worst parameter deviations. Column profiles based on the PWD also showed that the utilization of the adsorbent phase was maximized, resulting in the highest throughput per bed volume and the lowest solvent consumption.