What Do Desiccant Dryers Do?

A build-up of water in an air compressor system can wreak havoc on equipment and processes. Air dryers help to prevent this by removing moisture from compressed air before use.

Desiccant dryers contain two towers filled with hygroscopic material such as silica gel or activated alumina (molecular sieves). This material has surface pores that attract and remove moisture through a process called physisorption.

They Remove Moisture

You’ve probably seen packages of new electronics, medicines or clothing that have a small mesh packet of hygroscopic silica or activated alumina inside. These help keep the products dry during shipment and storage until they are needed, protecting the contents from moisture.

Desiccant air dryers use a similar method to eliminate moisture from compressed air. As the wet compressed air passes over the desiccant material, it adsorbs the water molecules through either physisorption or chemisorption. The air is then dried and ready for use.

They Prevent Corrosion

In a twin tower desiccant dryer (also called regenerative desiccant), compressed air passes through two vertical tanks filled with a bed of media such as activated alumina, silica gel or molecular sieve. As the air is cooled, it draws moisture into the desiccant, which slowly becomes saturated through a process known as adsorption.

When the desiccant reaches its saturation point, it’s regenerated using dry air purge or heat to drive off the adsorbed moisture. Then, the spent desiccant is purged and replaced with fresh media, and the cycle begins again.

Reduce Compressor Maintenance

Dryers help reduce maintenance by removing the extra moisture that would otherwise build up in your compressor. Moisture is what causes wear and tear on your system, so reducing it will increase the life of your compressor.

To do this, a compressed air dryer works chemically by passing the air through a bed of desiccant that adsorbs the water vapor. The water vapor clings to thousands of pores in each bead of the desiccant material – most commonly silica gel or activated alumina. The desiccant can only absorb so much water vapor before it becomes saturated. At this point, either very low dew point compressed air or heated purge air is used to regenerate the desiccant.

They Help Prevent Equipment Failure

We’ve all opened boxes of new electronics, medicines or clothing and found a small mesh packet labelled “Desiccant, Do Not Eat.” Inside are hygroscopic beads (typically silica or activated alumina/molecular sieve) that attract moisture protecting the merchandise during shipment and storage. Desiccant dryers use this same technology to remove water from compressed air for industrial applications.

Regenerative desiccant dryers usually have two towers filled with a media such as silica gel, activated alumina or molecular sieve. The adsorption process takes place as the dry compressed air passes through one of the towers.