Variation of the local effective axial dispersion coefficient with bed height in expanded beds

The local axial dispersion characteristics are very important and fundamental for the analyzing, modeling and understanding of biomolecules adsorption performance in expanded bed adsorption. In this work, the local effective axial dispersion coefficients along the bed height of an expanded bed system with porous adsorbent particles, Streamline SP and DEAE, were determined by measuring residence time distributions (RTDs) using the tracer pulse-response method combining in-bed sampling technique. The decreasing trend of the local effective axial dispersion coefficient with the increase of bed height was identified. An empirical correlation for the variations of the local effective axial dispersion coefficient with bed height was developed by taking account of the complex effects of liquid and particle properties, liquid flow behaviors, particle movements and the local bed voidage and particles size variations.