In an adsorber vessel, the transfer of water from the flow of air to the molecular sieves takes place in the mass transfer zone (MTZ). The mass transfer zone is that section of the adsorber bed in which the water load from the air current is deposited on the drying medium, thereby reducing the level of humidity from the inlet concentration to that at the outlet. The width of the mass transfer zone is primarily a function of flow velocity, inlet and outlet concentration of the drying medium and the type of drying medium.
Figure 6.4.3.1
The mass transfer zone migrates with increasing saturation from the inlet side to the outlet side of the adsorber vessel. Once the upper limit of the mass transfer zone reaches the end of the adsorber bed, the break-through of moisture commences.
