Different Types of Dryer Systems

I am often asked about the different dryer systems available, and it’s a great question for anyone looking to install a new compressed air dryer or upgrade an existing system.

My typical response is, “What are you doing with your compressed air?”—which helps determine the level of performance needed.

The second part of the discussion involves assessing their current compressor. If the customer has recently upgraded the main component of their compressed air system, we may be able to rule out some initial concerns related to filtration and temperature reduction.

Then, only once these factors are addressed, we can move on to the different types of dryer units.

Main Categories of Dryer Units

Compressed air dryers generally fall into four main categories:

• Desiccant Dryers (Absorbent and Adsorbent)
• Refrigerated Dryers
• Membrane Dryers

Desiccant Dryers

Desiccant dryers are divided into two types: absorbent and adsorbent.

Absorbent desiccant dryers use a material that absorbs moisture until it dissolves. A common term for these materials is "deliquescent," which describes the dissolving desiccant used in single-tower dryer units. These dryers are among the most popular and were the original dryer systems we developed here at Van Air.

Adsorbent desiccant dryers work differently by trapping moisture within their physical structure until they become saturated. Once fully saturated, the desiccant must either be replaced or regenerated. These materials - such as silica gel, activated alumina, and molecular sieves - are used in regenerative dryers.

Regenerative dryers utilize adsorbent materials in a tower system, providing high performance until the desiccant becomes saturated. Depending on the configuration - either heatless or heated regeneration - part of the operation involves regenerating the material for continued use. Without this regeneration process, the desiccant would become fully saturated with water and stop functioning effectively.

Refrigerated Dryers

Refrigerated dryers work by cooling the compressed air to just above freezing, then reheating it to approximately 70–72°F, which results in 30–35°F of dew point suppression—a level acceptable for most applications.

This type of dryer is commonly paired with new compressors for two key reasons:

Heat Mitigation: Many compressor manufacturers offer a refrigerated dryer option to counteract the excess heat produced by the compression process. Without cooling, this heat causes excess moisture and operational issues.

System Protection: Without a dryer, moisture buildup in the compressed air system would lead to frequent service issues, often blamed on the compressor itself.

The main downside to refrigerated dryers is their constant energy consumption and the need for regular maintenance by a refrigeration technician. However, when operating correctly, they are highly effective in managing moisture levels in compressed air systems.

Membrane Dryers

Membrane dryers do not use electricity or desiccants. Instead, they rely on a series of small capillary passages to remove moisture using pressure reduction and mechanical separation.

A percentage of the system’s compressed air is used to purge the moisture, which is then vented into the atmosphere. Hollow fiber materials wick the entrained moisture to the outer layer of the cartridge, where depressurized air pushes it out.

While membrane dryers can be highly effective for small compressed air systems, they are not ideal for large-scale applications. Additionally, they require extensive filtration to prevent contamination, making pre-filtration a mandatory requirement for their proper function.

Recap of Dryer Types

Absorbent Desiccant Dryers

• Utilize a desiccant material that absorbs moisture until it dissolves into a brine.
• Require regular draining and replenishment of desiccant material.
• No energy consumption, making them a cost-effective solution.
• Effective for large-scale compressed air systems but not ideal for high-purity air applications.

Adsorbent Desiccant Dryers (Regenerative Dryers)

• Use materials like silica gel, activated alumina, and molecular sieves.
• Require either replacement or regeneration when saturated.
• Provide low dew points, making them useful for small-flow or intermittent applications such as paint booths, CNC machines, and laboratory equipment.
• Often not ideal for complete system solutions or high-flow applications.

Refrigerated Dryers

• Require electricity to cool and reheat compressed air.
• Reduce the dew point by 30–35°F.
• Designed to handle the high temperatures produced by modern compressors (200–250°F air exit temperatures).
• Require routine maintenance but effectively control moisture when operating properly.

Membrane Dryers

• Do not require power or desiccants.
• Use pressure reduction and mechanical separation to remove moisture.
• Best suited for small compressed air systems but require extensive filtration.
• Not commonly used for large-scale applications due to airflow limitations.

Why Choose Van Air Systems?

Van Air Systems has been a leader in the compressed air industry for 80 years, providing expert solutions for compressed air and gas treatment. Contact us today to learn why we are the trusted name in filtration and drying technology.