5.4.6.2. Internal hot regeneration


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Fig. 5.13: Adsorption material after 6-8 hrs drying time
With hot regeneration the drying and regeneration times are around 6- 8 hrs. During the long drying time the moisture deposits on the inner and outer surfaces of the adsorption material. To reverse this process heat must be brought from outside. If the regeneration temperature of the drying material
is exceeded by heat from outside, the surface energies that occur outweigh the adhesive forces in the drying material and the water evaporates. A small flow of regeneration air drains off the moisture.

The regeneration temperature depends on the pressure dew point of the regeneration air. The lower it is, the lower the regeneration temperature of the dryer.

With internal regeneration the heat is transmitted directly from a heater in the drying tank to the adsorption material. This happens in two phases:
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Fig. 5.14:
Op. diagram of an adsorption dryer,
internal hot regeneration
1st Phase

Drying tank B is slowly heated by the internal heating to the necessary regeneration temperature. If the regeneration temperature is exceeded, the moisture releases itself from the adsorption material. Approx. 2- 3 % of the dried flow of compressed air from the compressor relaxes and at slight pressure is directed through a diversion line through drying tank B. This flow of regeneration air absorbs the moisture and directs it out into the open through an outlet valve.

2nd Phase

In a cooling phase the operating pressure drops back to the temperature of the drying bed. A second diversion line opens for this purpose. Appro x. 5 % of the compressor FAD is directed through drying tank B. The internal heating is no longer operating at this point.


Features
    • Economical with high volume flows.
    • Simple dryer construction.
    • Little dried compressed air is required to regenerate the dryer.
    • Prefiltration of intake air.
      A pre-filter removes most of the oil, water droplets and dirt particles from the compressed air.
    • Postfiltration of dried compressed air.
      Drying materials taken with the compressed air from the drying tank must be filtered out of the compressed air.