Abdelaziz Toumi

Optimisation and control of chromatography

Chromatography has developed from an analytical technology to a well-established separation process in industry. It is the method of choice for difficult separation tasks especially when temperature-sensitive components or species exhibiting very similar thermodynamic properties are involved. Large-scale industrial applications have been reported from different industrial fields, e.g. in the petrochemical, pharmaceutical, bio-chemical, and also in the food industry. Chromatographic separations often cause a large fraction of the overall production cost, so efficient design and operation become mandatory when production cost matters for competitiveness. In this paper we present an overview of model-based techniques for optimisation and control of batch as well as continuous chromatographic separation processes. These methods also help to speed up process development which may even be more critical than the reduction of production cost.

FINITE HORIZON OPTIMIZING CONTROL OF ADVANCED SMB CHROMATOGRAPHIC PROCESSES

Abstract Simulated Moving Bed (SMB) chromatography is attracting increasing attention for complex separation tasks. Chromatography is the method of choice in different fields (e.g. in the production of fine chemicals and pharmaceuticals) if the components have physicochemical properties which differ little or are thermally unstable. In these cases, standard separation techniques as, e.g. distillation or extraction, are not applicable. Control of SMB processes is a challenging task, as these processes exhibit a strongly nonlinear behavior and are of hybrid and periodic nature. In this contribution, we investigate the optimizing control of the new advanced SMB-like processes Vari C ol and PowerFeed. The online optimization is based on a full rigorous process model. An efficient numerical approach for the solution of the control problem is described and the control performance is demonstrated in simulations of a benchmark enantiomer separation.

Optimal Operation and Control of a Reactive Simulated Moving Bed Process

Abstract In this paper, we investigate the continuous production of High Fructose Corn Syrup (HFCS) in a Reactive Simulated Moving Bed process (RSMB). The RSMB process combines a quasi-continuous chromatographic separation with an enzymatic biochemical conversion of glucose to fructose. For the equilibrium limited glucose isomerization such an integration is suitable. The optimal operation of the RSMB process is determined using a sequential approach based on a rigorous mathematical model of the plant. In addition, we propose a new strategy to determine the distribution of the columns over the zones in the RSMB plant circumventing the solution of a Mixed Integer Nonlinear Problem (MINLP). During the operation of the RSMB process, disturbances occur (e. g. continuous decrease of the enzyme activity) which lead to an off-spec product. The control objective is to maintain the product purity while injecting a minimal additional amount of eluent. We propose a nonlinear model predictive controller which can deal with the complex hybrid dynamic of the RSMB plant as well as with hard constraints. The parameters of the non-linear process model are periodically estimated by least-squares fitting to online measurements. The efficiency of the whole control concept is shown in simulation studies for a 6-column RSMB plant.

Optimization and control of chromatography

Chromatography has developed from an analytical technology to a well-established separation process in industry. It is the method of choice for difficult separation tasks especially when temperature-sensitive components or species exhibiting very similar thermodynamic properties are involved. Large-scale industrial applications have been reported from different industrial fields, e. g. in the petrochemical, pharmaceutical, biochemical, and also in the food industry. Chromatographic separations often cause a large fraction of the overall production cost, so efficient design and operation become mandatory when production cost matters for competitiveness. In this paper we present an overview of model-based techniques for optimisation and control of batch as well as continuous chromatographic separation processes. These methods also help to speed up process development which may even be more critical than the reduction of production cost.

SMBOpt: A Software Package for Optimal Operation of Chromatographic Simulated Moving Bed Processes

In the last years, the Simulated Moving Bed (SMB) technique has increasingly been applied to isolate and purify high-valued pharmaceutical substances or fine chemicals and biotechnology products [13, 12, 9]. SMB-Processes are governed by mixed continuous and discrete dynamics and exhibit a complex behavior due to non-linear multi-component adsorption. Such processes cannot be easily designed and operated in the optimal way based solely on experience. In order to reduce separation costs and to shorten the overall design and development stages, a new integrated software package for the optimal operation of SMB-Processes is presented in this contribution.

Optimierungsbasierte Regelung eines integrierten reaktiven chromatographischen Trennprozesses (Optimization-based Control of a Reactive Chromatographic Separation Process)

Abstract Dieser Beitrag beschäftigt sich mit der Prozessführung eines chromatographischen Trennprozesses, bei dem kontinuierlich ein Fruktose-Sirup aus einer reinen Glukoselösung gewonnen wird. Glukose wird hierbei enzymatisch zu Fruktose umgewandelt. Gleichzeitig wird das so entstandene Zuckergemisch chromatographisch aufgetrennt. Die Prozessführung ist aufgrund des ausgeprägten nichtlinearen Verhaltens schwierig. Aufbauend auf einem rigorosen Prozessmodell, dessen Parameter on-line aus Messungen geschätzt werden, wird in dieser Arbeit ein nichtlinearer modellprädiktiver Regler entwickelt. Ziel der Regelung ist die Minimierung des Lösungsmittelverbrauchs bei Einhaltung der Produktreinheit. Es handelt sich also um eine echte On-line-Optimierung. Das gesamte Regelungskonzept wurde an einer Sechs-Säulen-Technikumsanlage implementiert und experimentell verifiziert. Dies ist die weltweit erste Realisierung eines MPC-Konzepts an einer SMB-Anlage.