Simulation of compression effects during scaleup of a commercial ion-exchange process

Abstract

A modified version of the general nonlinear multicomponent rate equation chromatography model has been developed to simulate compression effects on system behavior. It accounts for the variations in porosity and particle deformation that occur within a packed bed during compression. This paper investigates the effect of compression on the scaleup of a commercial packed- bed ion-exchange process to manufacture a whey growth factor extract (WGFE). The resin employed in the ion-exchange process is Sepharose Big-Beads SP (Amrad-Pharmacia, Sydney, Australia). Compression-induced changes in packed- bed porosity and particle diameter for a laboratory- (2 cm) and a production- scale (20 cm) column were estimated from pressure-drop data by using a modified volume-averaged continuum theory. These were combined with model parameters from a previous experimental study for two major whey proteins, lactoperoxidase and lactoferrin. Model simulations were performed. First, model parameters were validated by replication of experimental frontal adsorption breakthrough and step-elution curves. Selection of numerical parameters and accurate adsorption equilibria were identified as critical steps in ensuring successful reconciliation of model predictions with experimental data. The effect of compression on frontal adsorption and elution steps during scaleup was then investigated. For both frontal adsorption and step elution, system behavior was found to be largely independent of compression. Increased compression created only minor and trivial variations in effluent concentration profiles. These were influenced by two competing mechanisms, namely, premature breakthrough and increased external film mass transfer. Further simulations with a smaller particle size and superficial velocity displayed no significant increase in compression effects. Compression effects are not important during scaleup of this system.