Optimal design of direct recycling partial-discard strategy for enhancing the separation performance of the simulated moving bed process

Abstract

This study proposes direct recycling partial discard (DRPD) as a novel operating strategy and analyzes its potential to enhance the separation performance of simulated moving bed (SMB) processes by a simulation study. The DRPD strategy allows simultaneous removal and recycling of products through asynchronous port switching. Applied to the separation of S-(+)-GUA and R-(−)-GUA enantiomers, DRPD outperformed conventional SMB, VariCol, and VariCol + ModiCon operations in purity, recovery, productivity, and eluent consumption. Analyzing 542 DRPD operations with variations in the average column length (N¯k) and recycle length (RL), this study emphasized the significant roles of N¯I, N¯III, and RL values in process design. Consistently, the optimal conditions for the 5-column DRPD operation were determined atN¯I = 2.2, N¯III = 1.6, and RL >35% to maximize the throughput. The flexibility in the separation region of DRPD enabled a more significant difference between m3 and m2, expanding to m2 = 0.05, m3 = 4.84 compared to m2 = 1.81, m3 = 4.24 in SMB under the optimized setting. As a result, the optimal 5-column DRPD operation demonstrated substantial improvements in productivity and eluent consumption compared to the optimal 6-column SMB by 171.07% and −77.78%, respectively. Furthermore, an alternative design for the DRPD operation that can be implemented without additional equipment is proposed.