Air Dryers

In an earlier section of this course, we discussed the need to reduce dew point of compressed air so that it can be safely used in pneumatic control systems. There are a few other reasons to remove as much moisture from the compressed air as possible. Some of the important concerns are:

a. Moisture from compressed air can condense in air lines and air tools.

b. Condensation can cause damage to equipment by corrosion, freezing, and water hammer.

There are three basic designs of dryers: two absorption types and a condensation type. One type of absorption unit consists of two towers, each containing absorbent material. Reactivation is accomplished by means of electric or steam heaters embedded in the absorbent or by passing dried process air through it.

Another type of absorption unit consists of a single tank or tower containing a desiccant (drying agent) that dissolves as it absorbs moisture from the air and drains from the unit with the condensate.

The third type removes moisture from the air by condensation through the use of a mechanical refrigeration unit.