Hygroscopic plastics must be dried before processing. For this purpose different drying systems are available. The group of dry air systems includes the so-called compressed air dryer.
Instead of air dehumidified in adsorption dryers, this system uses pre-dried compressed air, which is decompressed, heated, and then distributed in the material container. With compressed air dryers can reach a dew point of -20 °C and lower. Compressed air dryers are suitable for small and large quantities. The energy-efficient further development of the compressed air dryer is the two-circuit compressed air dryer. These systems use ambient air and / or exhaust air to preheat the granules and require only a fraction of compressed air compared to conventional compressed air dryers to provide a dry atmosphere.