This is the simplest type of Air Dryer with Activated Alumina / Molecular
sieves Drying agent. Investment wise also this is the cheapest. This design is virtually
maintenance free, fully automatic, and requires no attention for years. Cold regeneration
type dryers do not require any heating for re-generation and therefore are very
simple in design and smooth in operation.
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In Cold regeneration Dryers, two vessels filled with desiccant are provided, which
cycle automatically, producing Dry air continuously. In these units, wet air enters
the bottom of one vessel and passes upwards through the desiccant bed where the
moisture is adsorbed. The dry air comes out from the top. A small portion of Dry
air is passed downward through the desiccant bed in the second vessel, which is
under re-generation. Moisture laden purge air is then vented out to atmosphere.
The purge loss is around 7.5% of the total air flow. At preset interval, the vessels
changeover automatically, and Dry air is available continuously, without any surges,
The purge air requirement is around 20% if (-)800C dew point is needed.
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