Membrane-type dryers are gas-separation devices. They consist of miniature membrane tubes made of plastic materials compounded to allow water vapor to pass through when there is a vapor pressure differential. The dew point ranges between +2 deg C and -8 deg C.
The making of membrane dryers dates back to the 1950's. It was based on ceramic technology. The tube sucks moisture from the surrounding area. And then, the water molecules pass through the tube to be carried away by natural air circulation. Migration of molecules takes place because of difference in partial pressure existing on the outside and inside of the tube.
Membrane Dryers Process
- The compressed air passes through a bundle of hollow membrane
fibers into the pressure vessels.
- Then the water permeates the membrane walls creating an
- Purge air is introduced and the equilibrium is destroyed.
- The dried air continues down the tubes and into the downstream air system.
The membrane dryer can last long and has no moving parts. The compressed air is 100% clean and oil free. These are noise free and can be placed at any orientation.
The main drawback is the relatively large amount of costly and unrecoverable compressed air lost through the membrane walls along with the water vapor. The dryer is so compact that it is difficult to clean it, hence it has to be replaced.