Steady-State Recycling Chromatography

Concerning its performance, steady-state recycling chromatography can be seen as an intermediate between simple batchwise or CLRC operation and continuous simulated moving bed (SMB) processes (Section 5.2). It combines lower complexity and equipment requirements than an SMB system with higher productivities and lower eluent consumption than obtained in batch chromatography. 

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Quinones, I., Grill, C.M., Miller, L., and Guiochon, G., Modeling of separations by closed-loop steady-state recycling chromatography of a racemic pharmaceutical intermediate,. Chromatogr. A, 867, 1, 2000. 

Sainio, T. and Kaspereit, M. (2009) Analysis of steady state recycling chromatography using equilibrium theory. Sep. Purif. Technol., 66, 9-18. 

The principles of closed loop as well as steady-state recycling chromatography have already been explained in Sections 5.1.3 and 5.1.4. In general, these process schemes may be chosen if for standard batch chromatography the number of plates has to be increased in order to get an efficient separation and the column length is restricted by the maximum allowable pressure drop. At the column outlet certain volumes of pure products are separated while the rest of the mixture is recycled to the column inlet. Through this a virtually longer column is achieved and maximum pressure drop is not exceeded. 

Kaspereit, M. and Sainio, T. (2011) Simplified design of steady-state recycling chromatography under ideal and nonideal conditions. Chem. Eng. 

Grill, C.M., and Miller, LM. (2005) Steady-state recycling and its use in chiral separations, in Preparative Enantioselective Chromatography, 1st edn (ed. G.B. Cox), Wiley-Blackwell,... 

The feed injection is performed by an injection loop. Advantage of this method is that the loop can be filled during the elution of the column, so the accuracy of the injection can be combined with a single flow rate purification method. This method is the only way to perform the injection of crude material in a one-column steady-state recycling system. It is also the most suitable injection method in super critical fluid chromatography. The main drawback of this method is that... 

Chapter 2 presents the description of quantities needed to quantify separation in open systems with flow(s) in and out of single-entry and double-entry separators for binary, multi-component and continuous cheimcal mixtmes, as well as a size-distributed particle populatioiL Separation indices useful for describing separation in open systems with or without recycle or reflux are illustrated for steady state operation (Sections 2.2 and 2.3) those for a particle population are provided in Section 2.4. At the end (Section 2.5), indices for description of separation in time-dependent systems, e.g. chromatography, have been introduced. 

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