Study on the number of decision variables in design and optimization of Varicol process

As a variant of simulated moving bed chromatography, Varicol process can realize flexible adsorbent allocation through asynchronous shifting of inlet and outlet ports. In this research, the switching strategies for achieving one certain average configuration were investigated. It was found the system performance depends on the total number of switches of the four ports during one switching period and Simple-Shifting-Scheme (SSS) with four switches brings out the best performance. More importantly, SSS could be different schemes, different by a parallel shifting, but all of them result in the same performance, demonstrating that only three instead of four switching times are decision variables while designing a Varicol process. To make the design of SSS more solid, a systematic method for derivation of SSS is proposed and applied on the optimization of a Varicol process for enantioseparation of 1,1′-bi-2-naphthol and reduce the solvent consumption by 17% comparing with SMB.