Effect of dead volume on performance of simulated moving bed process

Abstract

The volume of surrounding equipments (pipe transfer lines and valves) in the simulated moving bed (SMB) unit, which is called the dead volume, is modeled as bed-head, bed-tail and bed-line. Since the dead volume can be significant especially in industrial-scale SMB units, the consideration of dead volume has been required for high performance operation. In this study, a simple and unified approach based on the method of characteristics (MOC), called the extended node model, is established to solve fluid concentration dynamics within dead volumes. The computational efficiency of the approach is evaluated for three case studies of a standard four-zone SMB process with a linear adsorption equilibrium model. Insertion of one zone to flush the fluid trapped in extract bed-line into the standard fourzone SMB improves substantially purity, while recovery is kept constant.

Simulated Moving Bed Chromatography: From Concept to Proof‐of‐Concept

“…The flush of dead-lines with pure product to avoid contamination is also described in the literature [204,205,214].…”

“…When assembling an SMB unit, one should take into account that tubing and other equipment will introduce dead volumes, and the distribution of pumps and valves may introduce dead volume asymmetries [37,[203][204][205]. These issues may considerably limit the SMB performance, particularly for high-performance small-scale units.…”

Optimal flushing flow rates in para-xylene simulated moving-bed considering geometric factor of dead volume

“…The adsorption bed is represented by a convection-diffusionreaction partial differential equation (PDE) with linear driving force (LDF) mass transfer and competitive Langmuir adsorption isotherms (Beste et al 2000;Dünnebier and Klatt 2000;Kurup et al 2005;Lim and Bhatia 2011;Lim and Jorgensen 2004;Lim et al 2010;Minceva and Rodrigues 2003). This one-dimensional (1D) SMB model assumes that the bed void fraction, particle radius and porosity are constant along the columns, the mass transfer coefficients are independent of the mixture composition, the thermal effect and pressure drop of beds are negligible, as well as the hydrodynamics are ignored in the radial direction…”

“…This study assumes that the thermal effect, pressure drop, and radial mixing inside dead volume are negligible. The dead volume is modeled by the 1D convectiondiffusion model (Jin and Wankat 2007;Katsuo et al 2009;Lim and Bhatia 2011;Lim et al 2010;Minceva and Rodrigues 2003;Zabka et al 2008):…”

“…The discontinuous feature of concentrations was represented by distinguishing three different stages like time events during one switching period, when the fluid trapped inside the bedline dead volume is flushed out (Minceva and Rodrigues 2003). A comprehensive dynamic SMB model including both extra-column and bed-line dead volumes in a 7-and 8-zone PX SMB was developed incorporating an extended node model (Lim and Bhatia 2011;Lim et al 2010).…”