Variable Flow Rate Operation for Simulated Moving Bed Separation Systems: Simulation and Optimization

Abstract

Variable flow rate operation is developed to increase simulated moving bed (SMB) separation. With this mode of operation, the average flow rates of all external and internal flows can vary with time. The separations of dextran T6 and raffinose and of 1,1‘-bi-2-naphthol enantiomers, representing linear and nonlinear equilibrium systems, respectively, are tested. They are modeled with the Aspen Chromatography simulator for a four-zone SMB with one and two columns per zone. A simplex double-layer optimization method with a pulse flow design strategy is developed to maximize the SMB separation. Variable flow rate operation improves the separation for both SMBs, but improvement is more significant for the one column per zone SMB. For the SMB with one column per zone, for the linear system, the extract purity increased from 85.3 to 91.4%, and the raffinate purity increased from 89.2 to 94.9%. For the nonlinear system, the extract product purity increased from 85.0 to 94.1%, and the raffinate purity increased fr...