One column chromatographs with recycle analogous to a simulated moving bed

Nadia J Abunasser, Purdue University


The separation of binary and ternary mixtures is studied in one column chromatographs with recycle analogous to different SMB configurations (Analog). The very flexible basic design of the Analog consists of one column and a number of mixed tanks equal to the number of columns in the corresponding SMB. This design gives lower purities than the corresponding SMBs because of mixing in the tanks. For example, in separation of fructose-dextranT6, the Analog to a one column per zone SMB at D/F = 4.15, gave a purity index of 88.4 opposed to the SMB's 97.1. Mixing can be reduced and purities of the SMB approached by splitting the tanks into smaller tanks. For the dextran-fructose separation, the SMB purities were reached when each tank was divided into 7 smaller tanks. Analogs are designed for many SMB configurations. In some cases, tanks have to be split in order to retain the improvement produced by the more complicated operating procedures. For example, the tanks in the Analog to the 2-feed SMB had to be split into 3 smaller tanks for it to perform better than the Analog to VARICOL. Analogs are also designed for a 5-zone SMB and SMB cascades performing ternary separations. The purities are lower in the Analogs because of mixing, and splitting the tanks increases the purities. Analogs with mixed tanks are also designed for thermally assisted SMBs. An unmixed tank is proposed as an alternative to splitting the mixed tanks similar to the system proposed by Mota and Araujo [9], except a constant volume tank is designed. These unmixed reservoirs increase the purity indices in the Analogs (for the separation of the binaphthol enantiomers at c F = 2.9g/l, PI increased from 89.2 to 95.1) with no increase in equipment or desorbent; however; the purities still do not match the SMB purities because of dispersion in the reservoir. Scaling rules are applied to first increase the purities by reducing the productivity, and are then applied to increase the productivity by allowing the system to operate at the maximum allowable pressure drop while keeping purities constant.




Wankat, Purdue University.

Subject Area

Chemical engineering

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