This study is concerned with an industrial application involved in the manufacture of the polymer Nylon] 2 which is polymerised from solid monomer particles. There exists interstitial air among those particles. Oxygen in the air is a strong inhibitor of the polymerization reaction and has to be eliminated from the packed bed of monomer particles before they are introduced into the polymerization reactor. This is done by injecting nitrogen into the packed bed from the bottom of the bed. The nitrogen spreads into the packed bed and displaces the interstitial air. This process is already being employed in the polymer processing industry. The present research focuses on how to make this oxygen elimination process more effective. Using a numerical method to optimize parameters that affect the oxygen elimination process in packed beds, such as the number of injection jets, their positions and angles, etc., saves time and reduces cost. However, the numerical model needs to be validated before carrying out such a parametric study. Therefore, the experiments on the fluid flow in a packed bed are conducted to validate the numerical model. The numerical model is also validated against the analytical results for a packed bed with simplified geometry. The numerical results agree well with the experimental data and the analytical results. The gas flow through packed beds is treated as flow through a porous medium, The resistance to the flow due to the presence of the porous medium is represented by an additional momentum sink in the Navier-Stokes equations. (c) 2005 Elsevier B.V All rights reserved.