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Abstract

Simulated Moving Bed (SMB) chromatography has been established as a powerful technology for, e.g., separation of chiral substances or fine chemicals. Although in many applications SMB outperforms classical batch chromatography, further improvements of this process are possible and, consequently, there are significant research offeorts devoted to the development of advanced operating concepts. An attractive apporach is to superimpose to the cyclic port switching porcess additional periodic changes during a shift period [1]. A promising development in this context is the ModiCon concept, which employs a periodic modulation of the feed concentration during each switching interval [2]. It was demonstrated that under nonlinear conditions this operation mode allows for significant improvement of both solvent consuption and productivity in comparison to conventional SMB processes [2,3]. Subject of this work is the study of important practical aspects that have to be considered in order to fully exploit the potential of the ModiCon concept. The most important problem to be considered is the inlet (feed) concentration-time profile ("feed profile"). An important question is related to the optimum shape of this feed profile when considering practical feasibility limits like solubility and shape of adsorption isotherms. This issue is addressed by a parametric study using numerical simulations. In real plants several effects prevent the introduction of ideal (i.e., sharp) feed profiles. It is shown both experimentally and by numerical profiles due to dispersion (mixing) and dead volumes of the plant, respectively. Besides the above, several specific demands arise when improving a practical implementation of the ModiCon concept. These are related to plant equipment, experimental determination of system-specific parameters, and verification of "position" and shape of the feed profile. As a conclusion, guidelines will be given concerning the application of ModiCon to a specific separation problem. References: [1] Zhang et al., Korean J. Chem. Eng. 21 (2004) 454-464. [2] Schramm et al., J. Chromatogr. A 1006 (2003) 77-86. [3] Schramm et al., Chem. Eng. Sci. 58 (2003) 5217-5227.