Back to Basics: Everything You Need to Know About Desiccant Dryers

Need clean, dry air? A compressed air dryer can do the trick! Like their name would suggest, dryers are very common pieces of compressed air equipment that play an essential role in drying your compressed air. Designed to reduce the amount of moisture in the compressed air, desiccant dryers in particular are essential for applications and processes that require very high air quality - or with applications requiring an ultra-low dew point, typically around -40°C /-40°F. Having air at a reliable, predictable dew point can be important for demanding applications in industries such as pharmaceuticals and food processing. Read more about how desiccant dryers work, as well as the types of desiccant dryer technologies, below.

What is Desiccant?

Open a box containing new electronics, medicines, or clothing, and often you find a small mesh packet with words such as “Desiccant, Do Not Eat.” Inside those packets are hygroscopic beads (typically silica or activated alumina) that attract moisture, protecting the merchandise during shipment and storage. Desiccant also has industrial uses, notably removing moisture from a compressed air stream. Water vapor is exchanged from the moist compressed air into the desiccant, drying the air and causing the desiccant to gradually be saturated with adsorbed water. The desiccant must be regenerated (the collected moisture is purged) to regain its drying capacity.

How Does a Desiccant Dryer Work?

The general working principle of desiccant air dryers is simple: moist air flows over hygroscopic material (desiccant) and is thereby dried. The exchange of water vapor from the moist compressed air into the desiccant causes the desiccant to gradually be saturated with adsorbed water. Therefore, the desiccant needs to be regenerated regularly to regain its drying capacity.

Is There Only One Type of Desiccant Dryer on the Market?

Actually, there are four types of desiccant dryers available - each with a specific method for regenerating the desiccant.

• Purge regenerated adsorption dryers ("heatless-type dryers") use expanded compressed air to purge moisture from the desiccant. They are best suited for lower air flow applications.
• Heated purge regenerated dryers heat the expanded purge air to improve purge efficiency and reduce energy consumption by 25% compared to heatless-type dryers.
• Blower regenerated dryers blow heated ambient air to regenerate wet desiccant. Since no compressed air is used, energy consumption is 40% lower than for heatless-type dryers.
• Heat of compression dryers regenerate desiccant with the heat naturally given off by the compressor, without consuming additional energy.

Are There Any New Developments Coming in Desiccant Dryers?

Yes, Atlas Copco developed and patented a revolutionary new solid desiccant called Cerades. Compared to granular desiccants, Cerades delivers higher air quality, lower energy and service costs, and health and environmental benefits. Compressed air flows straight through the Cerades structure, reducing pressure drop (up to 70%) in the dryer to save energy. It handles higher air flow that granular desiccant, so the dryer can be much smaller. Cerades is vibration resistant and can be mounted horizontally, so it works in applications that could not previously use a desiccant dryer. It also lasts longer than granular desiccant, doesn’t decay and break down into dust like granular desiccant, and delivers longer cycle times to improve energy efficiency and process productivity.

Want to learn more about desiccant dryers – or dryers in general? Contact an expert today!