Page 244 - Chiral Separation Techniques

222 9 Modeling and Simulation in SMB for Chiral Purification

Fig. 9-2. Scheme of a Simulated Moving Bed (SMB).

9.3 Modeling of SMB Processes

The modeling of SMB can be addressed by simulating the system directly, taking
into account its intermittent behavior, or by representing its operation in terms of a
true countercurrent system. The first model represents the real SMB and considers
the periodic switch of the injection and collection points. The second is developed
assuming the equivalence with the TMB, where solid and fluid flow in opposite
directions.
Models can be classified according to the description of the fluid flow as contin-
uous-flow models (plug or axial dispersed plug flow) or as mixing cell models.
Some authors considered mass transfer resistances by including a rate law, usually
the linear driving force (LDF) approximation [14]; others used the equilibrium the-
ory. Several authors carried out the modeling of the SMB considering linear equi-
librium isotherms, namely for the glucose-fructose separation [15]. Nevertheless,
SMB units usually operate at high feed concentrations in the region of nonlinear