Removing air from bagged bulk material is a major concern for the material handling industry. A common technique is the application of suction by means of a probe, right before sealing the bag. Recent industrial experience shows that, for some granular materials, the effectiveness of this de-aeration technique is limited, probably due to the reduction in permeability associated to the decrease in porosity. The goal of this project is to understand and to remedy this limited effectiveness. The hypothesis that has been handled in this work, is the creation of an over compressed bulb of granular material that prevents the complete suction of the excess air and limits the compaction of the material. The creation of the bulb is defined by the permeability of the material, since it has been decompressed, is very susceptible to the pressure. Therefore, the dependency of the permeability with the pressure is the main reason why the bulb is created. In order to solve the issues behind the de-aeration process, the bulb creation process is modelled using mathematical models, which describe the suction in a porous media under certain conditions. The first one is a steady model, which describes the final state of the suction. The other one is a transient model, consequently, it describes the entire suction process. Those models are solved using numerical methods, obtaining information about the suction behaviour in granular materials and the bulb generation. Finally, with the knowledge acquired, the same models are used to optimize the suction processes and propose a new method. The method, consist in a mobile probe that moves during the suction, reducing the over-compressed bulb behaviour.