Select the right air compressor dryer - Atlas Copco Sweden
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Select the right air compressor dryer

Air Treatment Compressed Air Wiki Drying How-To

In previous articles, we have covered the potentially harmful effects of condensation within a compressed air system. The following information explains why removing moisture is important, and which air compressor dryer is right for you.

 

Integrated air compressor dryers

Some air compressors come with an integrated aftercooler. This built-in component is essential for removing up to 70% of moisture. While protecting your investment, this drying element is suitable for most applications.

However, if you work in an environment that's exceptionally humid or an application requiring the driest possible air, you'll want to add a dryer. Deciding on the right equipment depends on your space and needs.

Why an additional dryer is necessary for your compressed air system

choosing a dryer for your compressed air system

Excess water vapor in compressed air is unavoidable. However, with the right air compressor dryer, you'll prevent damage to pneumatic machinery, piping, valves, and any other components. You'll also avoid potential contamination of end products.
To prevent unnecessary maintenance repairs and production shutdowns, it's recommended to properly implement an air compressor dryer. Adding this equipment keeps compressed air dry, clean, and suitable for your applications.

Read more on the importance of dryers in compressed air. Selecting the proper dryer to treat wet air is largely dependent on the specific requirements and moisture tolerance levels of your set-up.

A refrigerated air dryer is suitable for most industrial and manufacturing facilities. If you work in a laboratory, with spray paint, or with printing and pneumatic tools, a desiccant dryer is the right choice.

The following section goes further into the different types of refrigerated dryers. This information is meant to help you gain a better understanding of which option is most suitable for your operation.

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The difference between a non-cycling and cycling refrigerated dryer

For applications that require dry air, but do not call for a critical dew point, a refrigerated air dryer is a great option. This equipment is cost-effective and comes in a non-cycling and cycling, and VSD option to match your budget and set-up.

Non-Cycling Dryers

A refrigerated non-cycling dryer is an excellent cost-effective choice for anyone looking to improve their compressed air quality. The term "non-cycling" means this type of dryer constantly operates refrigeration. It also utilizes a hot bypass valve to redirect the coolant, even at a less than full load condition.

In a refrigerated air compressor dryer, the air temperature is lowered to 3° Celsius (37° Fahrenheit). This drop allows for water to move from a vapor state to dry air. Non-cycling dryers are simple and reliable machines, meaning they're easy to maintain.

This type of refrigerated dryer is affordable, and comes with a relatively low cost of investment. In addition, non-cycling dryers are quick and straightforward to install and operate. This accessibility makes them a market standard in performance and quality, while exceeding expectations.

A non-cycling air compressor dryer works well with any rotary screw compressor. If you use a piston air compressor, a high temperature version is recommended.

Since these machines run nonstop, energy consumption at full or low load is nearly the same. Therefore, these units are less energy efficient than other options on the market. If electricity costs are a priority, you may want to check out a cycling dryer.

Cycling Dryers

Unlike non-cycling dryers, this equipment uses additional components, including thermal mass and frequency controllers. These integrations allow a cycling dryer to turn on and off, based on compressed air demand.

Since these machines adapt to use and application, they're more energy efficient than a non-cycling dryer. They also come with a customer-oriented design, offering high performance and reliability.

While the initial cost of a cycling dryer is slightly higher than a non-cycling dryer, it's a worthwhile investment. They're very reliable, offer easy installation, produce minimal noise, and run efficiently. Cycling dryers are ideal if you're concerned about energy costs.

Due to their advantages, a cycling dryer is highly beneficial to any compressed air system. This point is especially true when considering the overall life-cycle cost of your set-up. If your applications need fluctuating air demand, this equipment is the right choice.

VSD Dryers

If efficiency and low cost of ownership are your top priorities, the recently introduced VSD dryers will be your best choice. Variable Speed Drive technology has been available for compressors for many years. Matching the compressor’s motor speed to the air demand, VSD reduces energy consumption by double digits. This technology is now also available for refrigerated air dryers. The motor speed of the compressor integrated into the dryer adjusts automatically to the air demand with the same energy and cost-saving results. A VSD dryer also ensures a low, stable low dew point and outstanding quality air at all times. 

Refrigerated vs. desiccant dryers

The biggest deciding factor regarding compressed air dryers is the application and desired dew point. As previously pointed out, refrigerated air dryers provide a dew point of 3° Celsius (37° Fahrenheit). This temperature is sufficient for most applications.

However, if exceptionally cold compressed air is important, a desiccant dryer is recommended. These regenerative dryers achieve up to -70 °C (-100 °F) as standard. This low temperature delivers clean, dry air.

Unlike refrigerated air dryers, desiccant dryers utilize desiccant beads or solid desiccant to absorb water vapors. During this process, vapors adhere to the desiccant without changing the air composition. Once the desiccant becomes saturated with moisture, a process of regeneration occurs.

This involves dry purge air, heat or a combination of both to dry the wet desiccant. This type of dryer typically uses a dual tower construction design. One tower dries the wet air, while the other tower regenerates and purges moisture.

Types of desiccant dryers

Regenerative desiccant air dryers are designed to lower temperatures to -20 °C (-25° F), -40° C/F or -70 °C (-100 °F). With this, there are various types of regeneration when it comes to desiccant dryers. The way air is cooled and dried, depends on the purge air used. Higher purge is necessary for a larger compressor, resulting in increased power consumption and life cycle costs.

Non-heated desiccant dryers

Desiccant compressed air dryers without heat use 16-25% of purge air. These machines are cost-effective, but the least efficient. When considering this type of desiccant dryer, it's important to account for the extra purge air for your compressor. This calculation is used to sufficiently provide compressed air for your set-up.

Heated desiccant dryers

Heated purge air desiccant dryers utilize either internal or external heaters, accounting for part of the drying process. This type of desiccant dryer reduces the amount of purge air for the regeneration process to less than 10%.

Due to its design and ability to cut purge air in the process, this dryer comes with a high initial investment. However, a heated dryer provides significant energy efficiency during its lifecycle.

With heated desiccant air dryers, the external purge air is raised to a high temperature and introduced to the desiccant. This process aids with the drying and regeneration process, and utilizes 0-4% of purge air.

In order to completely eliminate purge air in a heated desiccant dryer, you'll want to add a blower. This equipment circulates heated air throughout the desiccant. Due to efficiency gains, a blower heat desiccant dryer tends to be the most expensive option. However, this set-up provides the best return on investment regarding energy consumption.

The right choice for you

Whether you need a refrigerated or desiccant dryer depends on the specific air quality requirements for your application. Dryers play a vital role in achieving clean, dry air. They're important for preventing shutdowns and air contamination.

Investing in a proper drying system now provides substantial savings over the lifetime of the equipment while providing satisfactory results for your customers.

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