ProSim launches a new dynamic simulator of chromatographic Simulated Moving Bed processes
ProSim recently announced the release of SiMoBe, a specific software for dynamic simulation of chromatographic Simulated Moving Bed (SMB) processes, to help manufacturers and engineering firms improve process designs, increase process yield, improve quality, increase capacity and reduce operating costs.
SMB technology is used for a wide range of applications from the production of optically pure compounds to the purification of natural extracts.
More economical than traditional chromatographic techniques, SMB is a continuous separation process gaining greater and greater interest for applications in the fine chemicals, pharmaceutical or food industries. Considered as the process of choice for high purity separation such as purification of optical isomers (enantiomer), SMB presents some advantages over more conventional separation processes. Industrially the SMB has been widely used, particularly in sugar separations (fructose-glucose). In opposition to the "usual" (elution) chromatography, SMB is a continuous process and thus much more adapted to large-scale production. SMB processes, which are often complex and highly interactive, are difficult to design and operate.
The optimal design depends on various factors such as columns numbers, their length and diameter, flowrates, switching times between two feed or product points. Furthermore, due to the complex dynamic, the choice of good operating parameters is not easy. For these reasons a detailed, reliable and accurate dynamic model has been developed by ProSim. SiMoBe enables engineers to address a wide range of process design and analysis applications, from R&D to pilot plant and production. It includes screening of process alternatives, acceleration of process development, reduction of plant commissioning time, management of changes in feedstock or capacity, etc… The developed model takes into account several phenomena (transport and dispersion of the liquid solution in the moving phase, mass transfer between the solid phase and the moving phase, transport and diffusion of the liquid solution in the stationary phase. Between each column, the system of valves to feed the SMB, to inject eluent, to produce extract or raffinate, is also modeled. A specific algorithm has been developed to solve the resulting mathematical model based on a discretization in finite volumes and GEAR method for the treatment of the DAE system. As the discretization introduces a "structural" axial dispersion this phenomenon is also taken into account in the model. Detection and treatment of the events which can generate discontinuities were more particularly dealt with.
Process description
The separation processes by preparative chromatography provide possibilities to separate with a very high yield multi-components mixtures in which the components have various adsorption affinities. Potential applications are in agrochemicals, food, pharmaceutical industry, fine chemistry.... In these industries, the traditional separation processes (absorption, distillation column, liquid-liquid extraction,..) must be turned down because of the substances thermal stability or for economic reasons. Consequently, separation by chromatographic way appears to be competitive for very high purity separation, for delicate products with close chemical structures (isomer, enantiomers..) and even for relatively significant tonnages as in sugar industry (glucose, fructose…). In these techniques, the components separate because of their difference in propagation velocity in the liquid-solid medium.
Conventional processes of liquid chromatography are based on batch processes. In order to improve the separation efficiency and profitability, counter-current processes are desirable but the presence of a counter-current solid phase would lead to technical problems of solid transport which prove to be insurmountable. In this context, the simulated moving bed (SMB) appears a promising alternative since it allows separations on a large scale (high purity, relatively significant tonnage...), and a counter-current behavior, avoiding the problems inherent to a true moving bed. The moving bed simulation is carried out by connecting several chromatographic columns in series. The counter-current movement is simulated by moving the feed stream and the input/output connections in a cyclic way, on the whole columns sections.
Stéphane Déchelotte, ProSim, 132, route d'Espagne, F-31100 Toulouse, France. Phone: +33-5-62-87-11-30. Fax: +33-5-62-87-11-39. E-mail: stephane.dechelotte@prosim.fr.
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