Expanded Bed Adsorption (EBA) enables the protein recovery directly from cultivations of microorganisms or cells and preparations of disrupted cells, without the need for prior removal of suspended solids. The performance of an expanded bed is comparable to a packed bed/fluidized bed. To extend the EBA technology in industries, a better understanding of the expanded-bed behavior is necessary to maximize its efficient applications. In this work the steady state hydrodynamic behaviour of expanded beds particularly bed expansion/ average porosity was studied experimentally. Two models are used to predict the terminal velocity of particles: one is Stokes law and other one is Shiller and Naumann model. The experimental results are in close agreement with the predicted porosity of Stokes law followed by Richardson - Zaki equation than the other model.