Design of bypass-simulated moving bed chromatography for reduced purity requirements

Abstract

Bypass-Simulated moving bed (BP-SMB) chromatography, a process characterized by the possibility of over-purifying the raffinate and/or the extract product followed by blending with the feed, is studied. The BP-SMB provides additional degrees of freedom; the opportunity to increase productivity; increased robustness and operational flexibility compared to obtaining reduced purities directly from the SMB. Based on the local-equilibrium theory, explicit equations to calculate productivity are derived for systems following a linear isotherm based on the minimum switch time. It is shown that the BP-SMB offers productivity advantage compared to a reduced-purity SMB specifically at low purity requirements, high selectivity and high efficiency conditions. The effect of column efficiency and feed concentration for systems following non-linear isotherms are studied using numerical simulations. The production of high-fructose corn syrup, an industrial application of BP-SMB, is analysed. For the HFCS separation, it is shown that a BP-SMB operation while not providing any advantages in terms of productivity, provides operational flexibility and robustness.