Refrigerated vs. Desiccant Air Compressor Dryer: What's the Difference?

Air dryers are vital for ensuring the supply of high-quality dry air in various industrial applications, such as instrument air, service air, or process air.

While a clean and consistent supply of compressed air is essential, ensuring that this air is also dry is equally critical.

Atmospheric air naturally contains moisture, and the high temperatures generated during air compression further increase the air's moisture retention capacity. This excess moisture can cause internal component corrosion, moisture carry-over, and the accumulation of contaminants like dirt and biological materials, leading to production contamination.

In industries like food and beverage manufacturing, such contamination can result in significant financial losses due to consumer complaints, product recalls, reduced productivity, and damage to the company’s reputation. Therefore, manufacturers must have measures in place to prevent contamination from the outset.

Removing unwanted moisture is necessary to protect pipelines and fittings and maintain air quality at the point of use.

This is where air dryers come into play.

To dry compressed air, the two most common technologies are refrigerant and desiccant dryers. Both ensure the delivery of high-quality, dry, and contaminant-free air at the point of use, often with the aid of downstream filters.

In this article, we will explore the importance of selecting the right air compressor dryer and the key differences between desiccant and refrigerated dryers. We’ll also help you determine the best air dryer for your facility.

Why Is Choosing the Right Air Compressor Dryer Important?

Selecting the right air compressor dryer is crucial because it directly affects the quality of your compressed air, as well as your energy consumption and overall operational costs.

Before deciding on an air dryer for your facility, consider the following questions:

1. Am I working with a single air compressor system or multiple systems?

2. What is the total compressed air demand of my facility?

3. How dry does my compressed air need to be?

4. What is the minimum acceptable dewpoint (moisture level) for my application?

5. Which type of air dryer best suits my compressor's operating parameters?

What Is a Refrigerated Air Compressor Dryer?

Refrigerated air dryers are the most common type of air compressor dryers. They operate using the same cooling mechanism found in typical residential and commercial air conditioning units.

In a refrigerated air dryer, the compressed air is cooled to approximately +3 °C using an air-to-refrigerant heat exchanger. As the air cools, moisture condenses into water droplets. These droplets are collected in a water trap and removed through an automatic drain valve. The air is then reheated, reducing its humidity levels and trapping any remaining moisture as vapor.

What Is a Desiccant Air Compressor Dryer?

Desiccant air dryers, also known as adsorption dryers, are designed to produce extremely dry compressed air.

These dryers work by passing the compressed air through vessels filled with desiccant materials, such as Activated Alumina, Silica Gel, Molecular Sieves, or a combination of these. As the air flows through the desiccant bed, the moisture in the air is absorbed by the desiccant material.

One cost-effective desiccant technology is the Heat of Compression Rotary Drum Adsorption Dryer, which operates with zero air loss and consumes minimal energy (0.12 kW) to deliver exceptionally dry compressed air with a dew point of -40 °C.

Refrigerated VS. Desiccated Air Compressor Dryer: What's The Difference?

Application

While the refrigerated air dryer uses air from a refrigerant heat exchanger to remove water content from the compressed air, a desiccant air dryer uses a bed of desiccant materials to do the same.

Cost

Refrigerated air dryers don’t require substantial capital investment and come with low operational and maintenance costs. On the other hand, desiccant air dryers come with low to medium capital investment. However, their ultra-air-drying technology, which brings the pressure dew point to -40 and even -70 Celsius, makes the investment worth it. Desiccant dryers are available as Twin Tower Heatless or Heated Blower type and Adsorption Rotary Drum type.

Dew point

While refrigerated air compressors are capable of delivering pressure dewpoint of +3° Celsius, desiccant air dryers can ultra-dry compressed air and manage pressure dew points as low as -40 all the way going down to -70 Celsius.

Desiccant vs. Refrigerated Air Dryers: Which Should You Choose?

Refrigerated and desiccant air dryers are the most commonly used methods for drying compressed air. The choice between them depends on your specific application, budget, and the location of your air compressor system.

Refrigerated dryers are ideal for general applications where the primary goal is to prevent corrosion in pipelines and the formation of water droplets. These dryers feature modern technology that enhances energy efficiency and reduces costs. Additionally, the use of refrigerant gases with a low global warming potential (GWP) makes them environmentally friendly. They are commonly used in various manufacturing facilities, packaging plants, and similar settings.

Desiccant dryers, on the other hand, are better suited for industries or applications that require exceptionally high air quality with lower pressure dew points. They are ideal for instrument air applications, medical facilities, pharmaceutical industries, and textile and food factories, where the compressed air must be extremely dry to ensure the end products are free from contaminants and moisture.