Improvement of the performances of a tandem simulated moving bed chromatography by controlling the yield level of a key product of the first simulated moving bed unit

- Tandem SMB (R1 and R2 SMBs) for ternary separation was the subject of this study.
- Effect of the yield of R1 key-product on the tandem SMB performances was studied.
- There exists an optimal R1 product-yield leading to the best tandem SMB performances.
- The optimal R1 product-yield is controlled by the extents of the following factors.
- The reload of R1 product into R2 and (ii) The dilution of stream from R1 to R2.

One of the trustworthy processes for ternary separation is a tandem simulated moving bed (SMB) process, which consists of two subordinate four-zone SMB units (Ring I and Ring II). To take full advantage of a tandem SMB as a means of recovering all three products with high purities and high economical efficiency, it is important to understand how the separation condition in Ring II is affected by that in Ring I, and further to reflect such point in the stage of designing a tandem SMB. In regard to such issue, it was clarified in this study that the Ring I factors affecting the Ring II condition could be represented by the yield level of a key product of Ring I (YkeyRingI). As the YkeyRingI level became higher, the amount of the Ring I key-product that was reloaded into Ring II was reduced, which affected favorably the Ring II separation condition. On the other hand, the higher YkeyRingI level caused a larger dilution for the stream from Ring I to Ring II, which affected adversely the Ring II separation condition. As a result, a minimum in the desorbent usage of a tandem SMB occurred at the YkeyRingI level where the two aforementioned factors could be balanced with each other. If such an optimal YkeyRingI level was adopted, the desorbent usage could be reduced by up to 25%. It was also found that as the throughput of a tandem SMB became higher, the factor related to the migration of the Ring I key-product into Ring II was more influential in the performances of a tandem SMB than the factor related to the dilution of the stream from Ring I to Ring II.