Compressed Air Dryers 101 - Compressed Air Dryer Basics

Refrigerated VS. Desiccant Air Dryers

There are a few kinds of air dryers one will commonly find in the industry. However, the two kinds that dominate are

1. Refrigerated air dryers
2. Desiccant air dryers

Both of which Zorn Compressor & Equipment commonly sells and services. Let’s break them down by type to understand air dryers more in depth.

Refrigerated Air Dryers

Refrigerated air dryers are used in industrial applications where general, non-critical plant processes occur. Such as, mechanical work or locations where temperature remains above freezing.

These dryers have few special requirements, are generally low-cost, and are easy to maintain. As a general overview, these dryers take warm, moist air and cool it to a temperature just above freezing. This then condenses the water vapor into liquid water which is collected in a trap and discharged from the compressor system. What's left is only dry air to be reheated to room temperature and fed through an outlet back to the compressor for use.

There are two types of refrigerated dryers: cycling & non-cycling. Here's the difference:

Cycling Refrigerated Air Dryers

Cycling refrigerated dryers allow your system to cycle on and off based on the current compressed air demand. They automatically change their rate of cooling based on the rate of air flow through the system. These dryers are great for industries that see a varying compressed air demand over the course of a workday. These dryers are more mechanically complex and thus more expensive, but they provide larger opportunity for energy savings. They are also quieter machines and have proven to have longer lifespans.

Non-Cycling Refrigerated Air Dryers

Non-cycling refrigerated dryers are commonly used when your compressed air demand is constantly high. They are made to run continuously and cool the air at a constant rate no matter what the rate of air flow through the system. These tend to be less expensive and much simpler to operate than cycling dryers. Because of this, they can be much more reliable and easier to repair if something does go wrong with the system.

Desiccant Air Dryers

Desiccant dryers are generally used in more critical process situations that require the drying process to adhere to strict quality guidelines of the finished products. These dryers can achieve extremely low dew points and can be placed in colder climates for processes requiring super dry air. These dryers utilize desiccant beads to absorb water vapor within the air. The moisture collects in the pores of the desiccant beads.

Desiccant dryers can come in a variety of configurations including twin tower, heatless, blower purge, heat of compression, and rotary drum dryer setups.

Twin Tower Desiccant Dryers

Twin tower arrangements are the most common desiccant dryer setup. One tower focuses on drying the air while the other tower works on regenerating the desiccant. The tower drying the air utilizes purge air to release moisture from the system. If your desiccant dryer also requires a heater, it is at this point that the air leaving the drying tower is passed through the heater to create hot, dry air for the regenerating tower. The collected moisture is then discharged out of the system. Most manufacturing processes benefit from this dryer setup.

Heatless Desiccant Dryers

Heatless dryers are just as they sound- they do not utilize any outside sources for heat. These units utilize a back-and-forth process that allows them to use their own generated dry air to remove moisture from the desiccant material. A portion of the dried air from these units is used for regeneration and these dryers can achieve extremely low dew points. Heatless dryers are used for applications that require very clean, dry compressed air. Examples include the pharmaceutical industry, food processing applications, and manufacturing microelectronics.

Heated Desiccant Dryers

Heated desiccant dryers utilize heat from and outside source to power their operations. The most common type is a heat of compression desiccant dryer that utilizes heat from the compression process to regenerate the desiccant material. Heated desiccant dryers require more electricity usage but use about half of the compressed air for regeneration. Some common industries that utilize this type of dryer include healthcare sanitization, paint booths, food drying, and textile production.

Blower Purge

Blower purge desiccant dryers utilize a blower and rely on a combination of generated heat and ambient air to reduce purge air usage to regenerate the desiccant material. These units are considered energy efficient. Common industries that utilize blower purge dryer technology include chemical manufacturing and electronics manufacturing.

Rotary Drum

Rotary drum desiccant dryers utilize a continuously rotating "drum" that has an internal desiccant wheel that allows the desiccant beads to absorb any moisture. These units are considered energy efficient and are great for operations that require a strict dew point level without utilizing purge air. These dryers are commonly found in food processing applications, the mining industry, and drying processes within the construction industry.

Membrane Air Dryers

Membrane compressed air dryers utilize a concept of multiple membranes that the air passes through. As the air passes through these membranes, the membrane fibers diffuse the water vapor within the air, allowing the dry air through. These dryers are smaller, so they are great for point-of-use applications and facilities with tight space constraints. Applications such as automotive assembly, petrochemical industries, and fabric processing commonly utilize membrane dryers in their compressed air systems.

Considerations Before Purchasing

1. Location

What kind of climate is your facility located in? The outside environment plays a big role in the moisture levels in your system. A facility located in northern, sub-freezing temperatures versus one in the hot, humid south will require substantially different systems. 

2. Types of work performed

Are your operating processes more mechanical? Or do you require extremely dry air for applications such as sanitization or painting?

3. Load profile

How constant do you need your airflow to be? If your shop uses air more intermittently instead of constantly, this also dictates the type of dryer required.

4. Piping system

Is your piping system exposed to outside air? Then the impact of changing temperatures outside your facility will have an impact on your compressed air, even if you regulate the inside temperatures.

5. Class of air required

Does your facility require strict regulations on air production? Industries such as food & beverage, pharmaceuticals, and coating processes commonly must adhere to strict classifications of their air produced. This changes the necessary air dryer for their system.

6. Oversize or undersize?

Never undersize a compressed air dryer. This can cause more water vapor in the compressed air stream downstream from the dryer- which is the very thing you purchased a dryer to prevent! Oversizing your dryer is a safer bet, although it comes with its own precautions such as increased cost of operating & shorter lifespan. Dryers are designed to operate at full capacity. So, the lighter the load, the more stress put on the dryer and its controls.

Air Dryer Brands Zorn Supplies

Zorn commonly supplies a variety of top-quality brand air dryer solutions including the following:

• Nano
• Zeks
• Quincy
• Gardner Denver
• Parker
• Powerex

Visit our "Air Treatment" page to view the air dryer technologies, parts, and brands we can supply your company.

ZORN'S PROMISE

Zorn is the Midwest leader of custom, engineered compressed air and vacuum solutions. We provide the best customer experience by understanding your applications and needs and offering an unparalleled commitment to customer satisfaction. 

Our comprehensive product and service solutions keep you running 24/7.

• Reliable equipment
• Trusted brands
• Seamless, easy installation
• Post-sales support
• Local, 24/7 service

Our compressed air experts look forward to meeting you to discuss your equipment and support needs. Please contact us directly at (262) 695-7000 with any questions or to schedule service for your system moving forward.

Related Resources

• What is a Compressed Air Dryer?
• Zorn Equipment Rental Agreement
• 12 Days of Compressed Air Maintenance
• Spooky Compressed Air Warning Signs to Pay Attention To
• 10 Common Compressed Air Myths: Busted!
• Air Compressor Usage in Modern Manufacturing
• Spring Cleaning Checklist For Compressed Air
• Air Compressor Dew Point 101
• Zorn Compressor Contractor Brochure
• Heat Recovery 101

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