US Patent 7141172 Versatile simulated moving bed systems

Distributed valve simulated moving beds are described in which junctions located between successive columns interrupt the flow of process fluid between columns, and either transmit the process fluid through a zone bypass to a succeeding column within the same zone or, if the junction is located between zones, direct the process fluid to an input/output line that is dedicated to the particular zone that immediately follows the junction. At each step of the SMB's operation, the distribution of flows in each junction is modulated to accomplish movement of ports consistent with the SMB's design. Further described are simulated moving beds that contain one or more decoupled on-line regeneration zones. The regeneration zone is decoupled from the separation zones in the sense that it observes a step time (a “regeneration interval”) that is different than the step time observed by the separation zones of the SMB. Because the regeneration zone is “on-line,” the SMB need not be stopped to remove columns for regeneration. Because the regeneration zone is decoupled from the separation zones, the column can stay in the regeneration zone as long as needed to accomplish the regeneration, regardless of the step time observed by the SMB.