As the air passes through the bed of desiccant in the column the water vapour is attracted to the pores of the material. Here, because of the difference in vapour pressure, condensation occurs, the desiccant gradually ABSORBS the molecules of water eventually becoming saturated. During the condensation phase the latent heat of the vapour is given to the surroundings, the bed temperature rising slightly.
The compressed air passes up the column emerging at the top dried to the desired dew point. Regeneration, or removal of the water from the system, is brought about by taking the vessel off line and depressurising it quickly.

SD150: Portable Air treatment packages. Intrinsically Safe Compact Rugged design for petrochemical and powerstation usage.