SMB Chromatography with Variable Process Conditions

Continuous counter-current separation by SMB chromatography can improve process economics. Nevertheless, more advanced processes have been developed recently. They are all based on the standard SMB technology but operated under variable process conditions to reduce the costs of column hardware and stationary phase as well as for fresh eluent and eluent work-up. New trends and suggestions to improve the operation of SMB processes have been reviewed, for example, by Seidel-Morgenstern, Kessler, and Kaspereit (2008) and Kaspereit (2009). 

The VariCol approach, as introduced by Ludemann-Hombourger, Bailly, and Nicoud (2000), increases the flexibility of the continuous separation system by an asynchronous movement of the injection and withdrawal ports. Within a complete process cycle, this leads to mean numbers of columns per section that are typically non-integer. As the minimum number of columns per section in an SMB system is 1, it is possible in VariCol systems to reduce the mean number to virtually any value less than 1. Owing to the asynchronous shift of the inlet and outlet lines in a VariCol process it may even happen that, during a certain interval, there are no columns in a section. In this case the inlet and outlet lines of this section coincide in one valve block. By placing the outlet lines upstream from the inlet lines a pollution of the product lines is avoided. 

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