Page 264 - Chiral Separation Techniques

242 9 Modeling and Simulation in SMB for Chiral Purification

The vertex of a separation region points out the better operating conditions, since it
is the point where the purity criteria are fulfilled with a higher feed flow rate (and so
lower eluent flow rate). Hence, in the operating conditions specified by the vertex point,
both solvent consumption and adsorbent productivity are optimized. Comparing the
vertex points obtained for the two values of mass transfer coefficient, we conclude that
the mass transfer resistance influences the better SMB operating conditions. Moreover,
this influence is emphasized when a higher purity requirement is desired [28].

9.6 Operation of the SMB Unit

The SMB pilot unit used in this work is the Licosep 12-26 (Fig. 9-15). It is a continu-
ous chromatographic system constituted by 12 columns Superformance 300-26
(Merck) with 26 mm internal diameter and adjustable length (5–20 cm) connected in
series. These have a jacket which allows operation of the SMB up to 60 °C. Each col-
umn is connected with four lines (eluent, feed, extract and raffinate lines) and 48 two-
way high-pressure pneumatic valves allow the connection of the inlet-outlet lines of the
columns. Consequently, there are 12 lines of each type. At a given time, only one line
of each type must be opened. The eluent, extract, feed and raffinate lines are shifted
*
after a given time period, the switch time interval, t . For the 12-columns SMB config-
uration, a whole cycle is made of 12 successive periods allowing the different lines to

Fig. 9-15. The Licosep 12-26 Simulated Moving
Bed pilot unit.