Design and optimisation of a simulated moving bed unit: role of deviationsfrom equilibrium theory

The design of a simulated moving bed involves thermodynamic, kinetic and hy drodynamic aspects and requires the optimisation of several variables: plan t design variables, such as the column length and diameter, and operating v ariables, among them four independent flow-rates, the feed concentration an d the switch time. In this work we develop an algorithm to design both the unit and its operating conditions, with an overall view on equilibrium prop erties, efficiency and hydrodynamics, using a simple equilibrium stage mode l. In this way we determine the parameters leading to the highest possible productivity for a given separation, only requiring the knowledge of the eq uilibrium isotherms, the Van Deemter equation and a correlation for pressur e drop. The algorithm has been used to investigate the effect on the separa tion performance of some parameters, such as particle size and required pro duct purity, which are not considered by equilibrium theory. The results ha ve been compared with the predictions of equilibrium theory and the observe d deviations have been put in evidence and discussed. (C) 2000 Elsevier Sci ence B.V. All rights reserved.