5.4.6.4. Vacuum regeneration


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Fig. 5.17: Adsorption material after 6- 8 hrs drying time
Vacuum regeneration is a variation of external hot regeneration. As 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 vacuum regeneration atmospheric air is drawn with a partial vacuum into the drying tank. This flow of air heats externally. Vacuum regeneration occurs in two phases.
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Fig. 5.18:
Op. diagram of an adsorption dryer,
Vacuum regeneration
1st Phase

A vacuum pump draws in air from the outside. This flow of air is heated by a heating register and drawn through the drying tank. Once the regeneration temperature is reached, the water releases itself from the Adsorption material. The flow of regeneration air takes on the moisture and transports it into the open through an outlet valve.

2nd Phase

In a cooling phase the operating temperature drops back to the temperature of the drying tank. For this purpose the heating register is switched off and cold air from the atmosphere is directed through the drying tank.

Features
    • Economical with high volume flows
    • No additional compressed air consumption.
      No compressed air is taken from the system for regeneration.
    • Long utility time of drying agent.
      Thermal stress on the drying agent is low.
    • Energy savings through lower regeneration temperature.
    • Prefiltration of inlet 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.