(132c) Predictions of Protein Adsorption and Desorption in Liquid-Solid Circulating Fluidized Bed Ion Exchange System

Extraction of proteins from large scale industrial and biological broths have continued to evolve due to the advancement in genetic engineering and increased concern about environmental protection. Due to low concentration of protein in the broths and relatively low capacity of ion-exchange resins used for protein extraction, a liquid-solid reactor system which is capable of simultaneous adsorption and desorption of protein in a continuous mode is crucial for large scale production. Liquid-solid circulating fluidized bed (LSCFB) is an integrated two-column (downcomer and riser) system which can accommodate two separate processes (simultaneous adsorption and desorption) in the same unit with continuous circulation of the solid particles between the two columns.

A mathematical model was developed considering the protein adsorption and desorption kinetics, liquid-solid mass transfer and the hydrodynamics of the LSCFB, to predict the protein adsorption and desorption in LSCFB ion exchange system. Adsorption of protein onto the ion exchange particles was considered as external and internal mass transfer limiting. Film mass transfer co-efficient was calculated using correlation available in the literature and the effect of axial dispersion and intra-particle diffusion resistance were incorporated using a lumped parameter. The model was based on the assumption of homogeneous fluidization. The simulation results showed good agreement with available experimental data.

A parametric study was performed to better understand the influence of different operating parameters on hydrodynamics and mass transfer in LSCFB ion-exchange system. This modeling study can be easily extended in other applications of LSCFB.

Keywords: Liquid-solid fluidization, liquid-solid circulating fluidized bed, protein recovery, ion-exchange, modeling, simulation.