Desiccant Air Dryer

Desiccant dryers use nonconsumable chemicals such as silica gel or active alumina, and can remove almost all the moisture from compressed air. A desiccant adsorbs moisture on its surface and holds the water as a mono or biomolecular film. This way it dried the air. The method of regeneration, the process of removing adsorbed water from the desiccant, is the primary distinguishing feature among the various types of desiccant dryers. These dryers consume about 10% of the air supply produced by the compressor for regeneration of the desiccant bed.

Desiccant dryers come in twin tower and carousel designs with a desiccant media that will remove water from the air stream. The dual tower design allows one tower to dry the air while the other tower is regenerated.

Types of Desiccant Dryers
Heatless Desiccant Dryers
They use two identical drying towers, each containing a desiccant bed. Pressure dewpoints ranging from -40 to -100°F are achieved by directing the flow of saturated compressed air over a bed of desiccant. A master controller cycles the flow of compressed air between the towers. Maintenance costs are low because they have few moving parts, and desiccant can last 10 to 15 years if the air is prefiltered to prevent oil contamination.

Heated Desiccant Dryers
These dryers can be internally or externally heated. Dryers have desiccant vessels contain heating elements. Depending on the amount of heat applied, these types still require 2 to 6% purge airflow to produce a pressure dew point of -40°F. The less purge air used, the higher the cost of power to run the heaters. Maintenance cost and downtime can be higher.

Blower Purge Desiccant Dryers
These dryers uses a heater and a blower instead of compressed air for regeneration. The heat-of-compression dryer, specifically designed for use with an oil-free compressor, uses the hot compressed air to regenerate the desiccant and remixes this air back into the compressed air supply yielding the lowest energy costs for desiccant type dryers.

Turbo Desiccant Dryers
This is a single tower desiccant air dryer that works similar to the twin tower heatless dryer but with a much lower first cost and much lower operating costs. These units deliver pressure dewpoints as low as -40°F. It requires no purge and has no moving parts but consist of a blower.