Optimal operation of a pseudo-SMB process for ternary separation under non-ideal conditions

Separation of a ternary mixture using a pseudo-simulated moving bed (SMB) process to facilitate the simultaneous recovery of all three components was studied. This process is different from the conventional four-zone SMB as it is partly operated as a fixed-bed chromatographic set-up and partly as a traditional SMB but without any feed inflow. The effect of various non-ideal conditions, viz. varying mass-transfer rates, non-linearity in the adsorption isotherms and different feed compositions, on the system performance was studied. Comparative studies were done at optimal conditions for each case. Rigorous multi-objective optimization studies using the binary coded Elitist non-dominated sorting genetic algorithm with jumping genes as the optimization technique were performed. Subsequently, the process was applied for the separation of C-8 aromatics containing xylene isomers. It was endeavored to see whether p-xylene and ethylbenzene can be recovered simultaneously with the best possible purity from a single Pseudo-SMB. It was observed that it is possible to recover all the three components from a single unit at high purity but at reduced productivity using large volume of desorbent. Pseudo-SMB process could be very useful for small-scale ternary separations such as purification of drugs. (c) 2006 Elsevier B.V. All rights reserved.