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How it works: resin dryers

By 29 August 2019January 14th, 2020No Comments

Operation of a resin drying cycle

This raw material drying system works on the basis of hot air that is transported. During this process, the granules in this hot air stream lose all moisture thanks to the absorbent granules that are added to it.
The hair dryer removes the moisture from the air coming from the hopper.
Before the resin dryer is reached, the return air flows through the filter unit (or cyclone blower). This filter ensures that dust or foreign objects are removed from the air stream. A holder for the dust is mounted in the base of the cyclone blower.
The air continues from the resin dryer to the process chamber. Here, heating elements take the temperature of the air to the set process level.
The air flows from the process heating chamber to the drying funnel. Here it is blown through plastic granules towards the hopper diffuser. The warm dry air absorbs the moisture contained in the plastic materials and is vented through the upper part of the hopper.
Suction unit
filter unit
The hopper has a pneumatic sliding gate in the lower part for unloading. This is placed on the material outlet door of the drying funnel.
  • Phase 1: the plastic materials are suctioned and charged
    The suction unit sucks the plastic materials from the big bags or silos and
    transports them to the hopper via transport pipes and hoses.
  • Phase 2: drying cycle
    The drying cycle takes place in a closed continuous cycle.
    The process air is first filtered by the filter unit (or
    blower) and then treated with the resin dryer.
  • Phase 3: the air is treated
    In the resin dryer, molecular sieves absorb the moisture from the passing air stream.
    That is why the air that comes out of the resin dryer is dry (Dew point).
  • Phase 4: The air is heated
    The air flows from the resin dryer to the process heating chamber. Here it is brought to the desired process temperature.
  • Phase 5: The material is dried
    The treated air flows to the hoppers, where the materials are dried.
  • Phase 6: The material is transferred to the processing machine
    Now the plastic materials are transported either directly or indirectly (via a secondary hopper) to the processing machine.


RH Drying tower
LH Drying tower
Bottom process valve
Top process valve
Regeneration drawer
RH tower heating chamber
LH tower heating chamber
Resin dryer process filter
Resin regeneration filter
Process heat exchanger
Regeneration heat exchanger
Process Blower
Regeneration blower

1. Regeneration phase

Although the molecular sieves can absorb a lot of moisture, they must be regenerated periodically (recovery phase). During the regeneration phase, the molecular sieves are dried and the absorbed water is removed.

2. Heating phase

  1. The regeneration blower collects air from the environment (13).
  2. The air is blown into the tower that undergoes the regeneration cycle.
  3. In the tower it is heated by two regeneration heating elements.
  4. It then flows through the molecular sieves and absorbs all the moisture that is located there.
  5. The air is re-routed when the molecular sieves reach the set temperature of 200 ° C (or after a maximum reached interval of 3 hours)
  6. The cooling phase now begins, during these cycles the regeneration distribution valve is exchanged (11) and the regeneration heating elements are switched off.

3. Exchanging the resin dryer towers

  1. The regeneration cycle is restarted after the towers (1 and 2) have been exchanged. Alternation takes place between the two towers so that the drying cycle can be carried out without interruption.
  2. The towers are exchanged using pneumatic cylinders as soon as the set dew point is reached.

4. Cooling phase

  1. The air circulates in a closed circuit and is cooled.
  2. It cools the molecular sieves until the set temperature of 80 ° C is reached (or the maximum duration of 2.5 hours has been reached).
  3. Now the regeneration supply stops until the process in the tower has reached the set dew point.
  4. Now the towers can be exchanged.

5. Processing phase

During the process phase, the moist air that comes out of the hopper is dried as follows:

  1. The air flows through the process filter, which removes any impurities.
  2. The air flows to the process exchanger, where it is cooled.
  3. It is then sucked in by the process fans (12) and (13).
  4. The blowers increase the pressure of the air, which is then blown to the lower distribution valve.
  5. The lower distribution valve transports the air to the tower undergoing the process phase (*).
  6. In the tower, the air is blown through the molecular sieves, which remove the moisture from the air.
  7. When the air flows out of the tower, it is dry.
  8. The air in the upper distribution valve is now blown to the recuperator
  9. This now leaves the resin drier and is again fed into the hopper.