Regeneration air can be specified as volume flow per unit of time. To specify it as a percentage of overall flow is not acceptable for practical purposes.
a) Regeneration volume flow
Regeneration volume flow Vrf is determined by means of Formula 7.2.3.1 which, in practice, is sufficiently accurate given a pressure dewpoint Pdp = -40°C. The calculation is carried out, using the effective (gauge) operating pressure pi = po -1. For rough estimates, it is only necessary to use the first part of the equation, provided that the cycle value c is sufficiently large.
Formula 7.2.3.1
b) Regeneration air requirement expressed in %
Alternatively, the regeneration air requirement expressed as a percentage is determined using formula 7.2.3.2. In order to avoid misunderstandings, reference points for deviating parameters must be specified and always stated. In practice, the regeneration air requirement expressed as a percentage is often misleading and should, in principle, be avoided.
Formula 7.2.3.2
c) Deviating regeneration air requirement
The regeneration air requirement obtained using Formula 7.2.3.2, is based on a pressure dewpoint of Pdp -40°C. For other pressure dewpoints, the values in Diagram 7.2.2.1 apply and should be used. Adsorption dryer layout is designed in such a way that compressed air volume flow at the inlet of the adsorption dryer is considered to be the basic value. Regeneration air, on the other hand, is no longer available at the outlet of the dryer and must be considered a loss.
Diagram 7.2.3.1
For low pressure dewpoints accompanied by low operating pressures, a correspondingly high regeneration air requirement arises. This interdependence is shown by Diagram 7.2.3.1. Inlet temperatures above ti = 35°C were intentionally not covered by this diagram.
