Partial port-closing strategy for obtaining high throughput or high purities in a four-zone simulated moving bed...

The "partial port-closing" operation strategy for a four-zone simulated moving bed (SMB) chromatographic process for binary separation was developed to improve the SMB performance. This strategy included the partial extract-closing (PEC) and the partial raffinate-closing (PRC) operations. In case of the PEC operation, the extract port is made to be closed during the first-half stage of a switching period. During the latter-half stage, the extract port is made to be open. In case of the PRC operation, the raffinate port is made to be open during the first-half stage of a switching period. During the latter-half stage, the raffinate port is made to be closed. If the operating conditions are chosen properly in each operation using a highly efficient optimization tool, the product stream can be collected during only the period that the product is almost separated from impurity. During the other period that the product is contaminated with impurity, the collection of the product stream can be stopped by closing the product port. The uncollected product stream is then allowed to keep migrating through the adjacent zone within the SMB process. Such a partial port-closing operation including PEC and PRC was found to surpass a conventional SMB operation remarkably in throughput and product purity.