A desiccant dryer is a type of air dryer that uses a desiccant material (hygroscopic substance) to remove moisture from compressed air. The desiccant, which is most commonly activated alumina, absorbs the water vapor in the air. This allows the compressed air to be dry and clean, and can prevent mold and mildew.
Activated alumina is an aluminum oxide bead known for its remarkably porous structure and an impressive surface area-to-mass ratio. It is utilized in various applications and is what we see in the field 99% of the time.
Desiccant can also be made of molecular sieve which is made from a porous sodium aluminosilicate bead. When using molecular sieve you can achieve a dew point of -100° F and lower, where activated alumina generally is around -40°. Hitting these lower dew points is important in some cases for controls and instrumentation in some factories (we usually refer to these as critical application).
Silica gel is another desiccant you will see occasionally. It is also extremely porous and is really good at soaking up water, hydrocarbons, CO2, siloxanes, sulfur, and others. People often use it in tandem with a layer of activated alumina.
Types Of Dryers
Desiccant dryers come in a variety of types, including heatless, heated, and blower purge. Heatless dryers use the compressed air itself to regenerate the desiccant, while heated dryers use an external heat source to regenerate the desiccant. Blower purge dryers use a small blower to force air through the desiccant, regenerating it.
Heatless Dryer
Choosing The Right Desiccant Dryer
When choosing a dryer, it is important to consider the flow rate and pressure requirements of your system. You will also want to consider the dew point requirements and the operating environment. If the dryer will be exposed to harsh conditions such as high temperatures or vibrations, you may need to adjust your selection.
Dryer Maintenance
All dryers require regular maintenance to ensure optimal performance. This includes monitoring the pressure drop across the dryer, replacing the desiccant when necessary, and cleaning the air filter.
Overall, desiccant dryers are a reliable and effective solution for removing moisture from compressed air. They are widely used in a variety of industries and applications, and can help to improve the performance and longevity of equipment and processes.
