- Air permeation through a plug, moving in a vertical pipe with a constant velocity, was investigated theoretically. The preliminary experiments confirmed the feasibility of Darcy- Forchheimer's law for air flow through a plug. Although the experiments were conducted with granular materials, the theoretical investigation was expanded to include cohesive materials (powders). On this basis, a theoretical model that predicts the air velocity, pressure drop and plug velocity for conveying a cohesive plug in a vertical pipe was developed. Further experiments were conducted to characterize the conveying parameters of different particulate solids and to confirm the theoretical model. Pressure drop, air and plug velocities were examined as functions of different parameters. Parametric investigation showed that the plug velocity is lower than the gas velocity, due to the gas flow through the plug.