Henning Schramm

Simulated moving bed process with cyclic modulation of the feed concentration

The improvement of the simulated moving bed (SMB) process based on the introduction of a cyclic modulation of the feed concentration is described. It is demonstrated that such a feed concentration gradient during the shifting cycle can improve the performance significantly. The productivity and the product concentrations can be increased while simultaneously the solvent consumption can be decreased compared to the conventional SMB process with constant feed parameters.

Improving simulated moving bed processes by cyclic modulation of the feed concentration

A new mode of operation for simulated moving bed (SMB) chromatographic processes is presented. While conventional SMB processes are operated with constant feed concentration, a modulation of the feed concentration during the switching cycles is introduced in the new mode of operation. Thereby the performance compared to the conventional SMB process is improved significantly. The productivity and the product concentration is increased. Simultaneously, the solvent consumption is decreased.

Optimal operation of simulated moving bed chromatographic processes by means of simple feedback control

In this contribution, simple methods are presented for controlling a simulated moving bed (SMB) chromatographic process with standard PI (proportional integral) controllers. The first method represents a simple and model-free inferential control scheme which was motivated from common distillation column control. The SMB unit is equipped with UV detectors. The UV signals in the four separation zones of the unit are fixed by four corresponding PI controllers calculating the ratio of liquid and solid flow in the respective separation zone. In order to be able to adjust the product purity a second, model-based control scheme is proposed. It makes use of the nonlinear wave propagation phenomena in the apparatus. The controlled chromatographic unit is automatically working with minimum solvent consumption and maximum feed throughput--without any numerical optimization calculations. This control algorithm can therefore also be applied for fast optimization of SMB processes.

Optimization of solvent gradients for chromatographic separations

In this paper preparative gradient chromatography is mathematically described using a simple cell model. The model enables the simulation of single elution profiles as well as the systematic optimization of the operating parameters. Experimental investigations were carried out for the model system benzyl alcohol/2-phenyl ethanol/toluene separated on a RP18 stationary phase with mixtures of water and acetonitrile as eluant. In the experiments different linear changes in the eluant strength were applied.