SIMULATION OF COMPRESSION EFFECTS DURING SCALEUP OF A COMMERCIAL ION-EXCHANGE PROCESS

A modified version of the general nonlinear multicomponent rate equati on chromatography model has been developed to simulate compression eff ects on system behavior. It accounts for the variations in porosity an d particle deformation that occur within a packed bed during compressi on. This paper investigates the effect of compression on the scaleup o f a commercial packed-bed ion-exchange process to manufacture a whey g rowth factor extract (WGFE). The resin employed in the ion-exchange pr ocess is Sepharose Big-Beads SP (Amrad-Pharmacia, Sydney, Australia). Compression-induced changes in packed-bed porosity and particle diamet er 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 pre vious experimental study for two major whey proteins, lactoperoxidase and lactoferrin. Model simulations were performed. First, model parame ters were validated by replication of experimental frontal adsorption breakthrough and step-elution curves. Selection of numerical parameter s and accurate adsorption equilibria were identified as critical steps in ensuring successful reconciliation of model predictions with exper imental data. The effect of compression on frontal adsorption and elut ion steps during scaleup was then investigated. For both frontal adsor ption and step elution, system behavior was found to be largely indepe ndent of compression. Increased compression created only minor and tri vial variations in effluent concentration profiles. These were influen ced by two competing mechanisms, namely, premature breakthrough and in creased external film mass transfer. Further simulations with a smalle r particle size and superficial velocity displayed no significant incr ease in compression effects. Compression effects are not important dur ing scaleup of this system.