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 C8 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.