Sunday, January 29, 2023

What Is a Desiccant Air Dryer?

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Many industrial systems and tools use compressed air for power, but the reality of these compressed air systems is that air cannot be compressed and then immediately used as a power source. Raw, compressed air is often dirty and full of moisture, which must be removed before the air can be used. Otherwise, interactions between moisture, contaminants, and equipment can damage pneumatic equipment. Dry, clean air, on the other hand, poses little risk to air-powered systems, extends their useable lifespans, and can potentially lower operating costs.

In order to dry the air from an air compressor, many systems include industrial air dryers. There are two different types of industrial air dryers, refrigerated air dryers and desiccant air dryers. This post will provide a snapshot of the nature, operation, and utility of desiccant air dryers.

How Does a Desiccant Air Dryer Work?
While there are a few different types of desiccant air dryers (see below), the principle of operation is effectively the same. The regeneration process depends on the type of dryer, either heatless (pressure swing type) or heated (temperature swing type).

These industrial air dryer systems contain closed lines that contain and circulate the compressed air, as well as chambers bearing extremely hygroscopic desiccant materials. There is a wide range of different types of desiccants, including but not limited to silica gel, activated alumina, calcium chloride, molecular sieve (sodium aluminosilicate), and others.

In general, these desiccant materials consist of very small particles or desiccant beads (adsorbents) with a very high surface area to volume ratio, and they tend to have a very high porosity as well. Deliquescent desiccants (absorbents) are formed tablets. All of them are extremely effective at adsorbing or absorbing moisture from the air, and some of them are able to remove certain other contaminants, such as suspended hydrocarbons, as well.

With the water vapor removed, the dried compressed air can then be delivered to the rest of the system as a power source for a wide range of industrial applications, ranging from the operation of handheld tools to the actuation of pneumatic machinery.

Is There More Than One Type of Desiccant Air Dryer?
While all desiccant air dryers use some form of physical desiccant, there is some variance in how they operate. The following are some of the more common types of desiccant air dryers.

● Regenerative Compressed Air Dryers: Regenerative desiccant dryers consist of heatless, externally heated and blower purged air dryers. Typically, regenerative air dryers contain two cylinders or “dual towers,” (sometimes also called twin towers) containing desiccant beds. Typically, wet compressed air only flows through one; when that tower’s desiccant load becomes saturated, the system switches and runs air through the other tower until the desiccant in the other tower is “regenerated” and once more ready to be used.

● Single Tower Deliquescent Dryers: A single tower deliquescent desiccant air dryer pushes raw compressed air through a cylinder that contains desiccant materials; these materials capture water as it “deliquesces” and absorbs it. These desiccant air dryers are convenient and feature simple operation and require no utilities. They absorb water, dissolve it and then drain it to the bottom of the chamber, consuming the desiccant. The deliquescent desiccant is then refilled as required to keep the vessel at the required level.

● Non-Regenerative Cartridge-Type Air Dryers: Non-regenerative cartridge-type desiccant air dryers are similar to single tower deliquescent air dryers in the sense that the dryer does not have regeneration capabilities and must be replaced when saturated. However, the cartridge type dryers are mostly used in small flow applications for instrumentation or critical tools and machinery.

Consult Air & Vacuum Process, Inc. for More Information
If you still have questions about compressed air treatment or the different types of desiccant air dryers that are commonplace in the industry, visit Air and Vacuum Process, Inc., at For over two decades, Air and Vacuum Process, Inc., has been serving customers around the world with leading natural gas and compressed air treatment solutions; consult their website for more information or contact them directly at [email protected] or by phone at 866-660-0208.

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