Using a compressed air system comes with the challenge of moisture buildup - especially in environments with low dew points and high humidity. And while most dryers remove moisture as a core functionality, different types of air dryers do so in different ways, and some even require additional drying. That's where desiccant beads come into play.
You've most likely seen desiccant beads at work in your shoe box, medication package, or in any electronics in a mesh bag that says "DO NOT EAT" But these aren't only used for consumer goods; they're widely used in compressed air systems as well.
In this article, we'll discuss what desiccant beads are and how they help remove moisture in compressed air systems.
What are Air Dryer Desiccant Beads?
Desiccant beads are materials used in compressed-air dryers to absorb and hold liquids and other gases. Air dryers use desiccant beads or cartridges to remove water vapor from an air stream, providing extremely dry air for critical applications and machinery.
Which Compressed Dryers Use Desiccant Beads?
Air dryers that use these materials are called desiccant air dryers. They're used in applications requiring drier air than other types of compressed air dryers can achieve in lower dew points. Which dryer is used will depend on the application, the dew point, and the environment.
Refrigerated air dryers, for example, can cool compressed air, condense water vapor into liquid, and drain excess moisture without using extra desiccant media. These are typically used in dew points as low as -50°F, where desiccant dryers can operate in dew points as low as -100°F.
Desiccant dryers come in a variety of configurations for different industrial applications, from point-of-use units for intermittent use to regenerative units for continuous use.
Comparing Types of Desiccant Beads Used in Compressed Air Dryers
The top three most common are:
- Silica Gel
- Activated Alumina
- Molecular Sieve
Not everyone is a desiccant dryer pro, so we've compiled what you need to know about all three types.
| Max Dew Point | Pros | Cons | Applications | Air Dryer Considerations | |
| Silica Gel | -40°F | Excellent adsorption in appropriate dew points, low cost, and widely available | Pre-filtration requirement; less effective in high heat | General purpose/intermittent use (spray paint, auto body shops, tools) | Air filtration system required |
| Activated Alumina | -40°F | Durable, resistant to liquid water | Requires larger vessels due to a larger bead size, less adsorbent at extremely low dew points | Continuous compressed air systems (industrial equipment, manufacturing facilities, CNC machining, plasma cutting) | Air filtration system required |
| Molecular Sieve | -100°F | Best moisture adsorbency in dry environments, less storage capacity required | Continuous-use Higher upfront cost, pre-filtration, and maintenance still required | Continuous-use critical process air (food packaging, pharmaceutical production, outdoor winter air systems) | Filtration and maintenance recommended |
SIlica Gel
Silica gel is most commonly used in packaging because of its ability to adsorb moisture quickly with little or no pressure. In an air system, it can offer excellent adsorption providing dew points down to -40°.
However, this ability to rapidly attract water vapor can be affected when in contact with liquid water. When completely saturated, the bead will crack into small fragments. These smaller fragments will migrate downstream in your air system.
This media migration (small fragments and dust) can cause significant downstream damage to your equipment or the performance of your applications that lack pre-filtration.
Activated Alumina
Activated Alumina is a porous form of aluminum oxide. Activated Alumina provides high adsorption capacity, dew points down to -40°F, and resistance to the breakdown that silica gel experiences when exposed to liquid water or high saturation levels of water vapor.
However, Activated Alumina does “dust” when subjected to pressure swings and pulsations within a compressed air system.
Typically, a larger bead in a well-performing system utilizing activated alumina will require larger vessels (more space) to achieve the same results as its smaller competitors.
Molecular Sieve
A molecular sieve is a small, sodium aluminosilicate bead. When used in an air dryer, molecular sieve can reach dew points as low as -100°F.
This media does not fracture when submerged in water or exposed to high levels of water vapor. As a smaller bead with a very high surface area, it requires much less storage capacity to dry the same volume of compressed material as its counterparts.
The cost of Molecular Sieve is often higher than that of Silica Gel or Activated Alumina, but this cost can be justified by its increased longevity and higher performance. This type of media is used in mid-range to advanced desiccant dryers.
Tsunami Desiccant Dryers: Core vs. Pure vs. Ultra Series
Tsunami offers several types of desiccant dryers, each best suited for specific conditions and applications.
- CORE: This 25 CFM dryer is built for intermittent use and features a replaceable desiccant cartridge, simplifying maintenance and operation. Its proprietary desiccant blend reduces dusting and tunneling.
- PURE: A mid-range dryer, this product uses molecular sieve and automatic desiccant regeneration to avoid manual refills. This dryer is suitable for a broader range of applications than CORE and higher airflow demands.
- ULTRA: Tsunami ULTRA regenerative dryer has the same capabilities and uses the same desiccant media as PURE, but uses programmable controllers for more advanced applications rather than timer-based controls.
Is a Desiccant Dryer Right for Your Project?
The type of desiccant media used in a compressed air dryer will directly impact the performance, quality, and ultimate product choice. Understanding how they work will help you and an experienced manufacturer decide on the appropriate desiccant dryer for your application.
Curious to learn more about Tsunami desiccant dryers? Download the Tsunami product catalog to get more technical information on each dryer, or reach out to an expert to discuss your specific needs.
