Optimization of simulated moving bed and Varicol processes.

A new continuous chromatographic process (Varicol) has been presented recently. Its basic principle consists, in contrast to the traditional simulated moving bed (SMB) technology, of an asynchronous shift of the inlet/outlet lines in a multi-column system with a recycle loop. Due to the stronger influence of the discrete dynamics on the plant behavior, the design of a Varicol process requires the use of model-based optimization to take advantage of the very high flexibility of this process. The equilibrium theory which has been successfully applied to SMB by many practitioners fails to predict the region of complete separation accurately. In this paper, we present a rigorous model-based optimization framework, which can handle the SMB and the novel Varicol process in a systematic manner. The feasibility of the approach is demonstrated by the separation of a mixture of propranolol isomers which exhibits a highly non-linear multi-component adsorption behavior. Experimental results are presented and discussed.

Application of the "VARICOL" process to the separation of the isomers of the SB-553261 racemate.

A new continuous chromatographic process (VARICOL) has been presented recently. The basic principle of the new VARICOL process consists of an asynchronous shift of the inlet/outlet lines in a multi-column system on a recycle loop. This process has been used to perform the separation of the optical isomers of the SB-553261 racemate. In this paper, we illustrate that for this specific separation, the VARICOL process is more efficient than the well-known SMB process.

Design and optimisation of a simulated moving bed unit: role of deviations from equilibrium theory.

The design of a simulated moving bed involves thermodynamic, kinetic and hydrodynamic aspects and requires the optimisation of several variables: plant design variables, such as the column length and diameter, and operating variables, among them four independent flow-rates, the feed concentration and the switch time. In this work we develop an algorithm to design both the unit and its operating conditions, with an overall view on equilibrium properties, efficiency and hydrodynamics, using a simple equilibrium stage model. In this way we determine the parameters leading to the highest possible productivity for a given separation, only requiring the knowledge of the equilibrium isotherms, the Van Deemter equation and a correlation for pressure drop. The algorithm has been used to investigate the effect on the separation performance of some parameters, such as particle size and required product purity, which are not considered by equilibrium theory. The results have been compared with the predictions of equilibrium theory and the observed deviations have been put in evidence and discussed.