The adsorption process with vacuum regenerated adsorption dryers is, in principle, identical to the methods previously explained in conjunction with heat regenerated adsorption, and is thus sketched here only by means of key terms.
Figure 5.6.2.1
With vacuum regenerated adsorption dryers, the dynamic capacity of the drying medium is utilised up to 18 - 20%, making use of the internal and external surface. Adsorption takes place with the direction of flow from bottom to top. The mass transfer zone migrates with increasing saturation from the inlet to the outlet of the adsorber. When the break-through point is reached, the system switches over to regeneration. The time cycles are dictated by economic considerations leading to adsorption and regeneration periods of 4 - 6 hours. With vacuum regenerated adsorption dryers, the temperature increase through heat of adsorption in the drying medium bed brings about an outlet temperature of the compressed air which, under normal operating conditions, is 12 - 20°C higher than approach temperature.
