What Are Air Compressor Dryers?

Everything you need to know about compressed air dryers

Air compressor dryers are essential to a compressed-air system, removing moisture from compressed air. Doing so prevents damage to equipment and maintains end-product quality in industrial applications. 

Different types of dryers exist, such as desiccant air dryers for achieving low dew points and refrigerated air dryers for cooling the air and condensing moisture. Choosing the right dryer is essential for ensuring dry, compressed air for your application. 

Today, we will explore the different types of compressed air dryers, their principles, advantages, and applications.

Why an Additional Dryer is Necessary for a Compressed Air System

An air dryer is a great way to maintain compressed air quality in industries requiring extra dry air. Moisture in a compressed air system can cause corrosion and equipment damage as well as contaminating end products. These issues are particularly significant in pharmaceuticals, food processing, and manufacturing industries, where uncontaminated dry air is essential. 

The Need to Dry Air Before it Enters Compressors

In the pharmaceutical industry, moisture can degrade ingredients, leading to poor product quality and potentially hazardous outcomes. Similarly, in food processing, excess moisture can promote the growth of bacteria, posing health risks to consumers. To mitigate these issues, implementing the correct type of air dryer in your compressed air system is vital to maintaining air quality. 

How Does a Compressed Air Dryer Work?

Compressed air dryers extract moisture out of the air through processes known as adsorption and refrigeration. In the adsorption method, the compressed air enters through a desiccant material that attracts and holds onto water molecules. This process effectively removes moisture, ensuring high-quality air without contaminants. 

During drying, the air temperature drops due to the cooling effect of removing moisture from the compressed air. In refrigerated dryers, the air is cooled using a heat exchanger and passed through a condenser to remove any remaining water vapour.

Different Types of Compressed Air Dryers

This section provides a clear and comprehensive guide on the different types of compressed air dryers available.

Refrigerated air Dryers

A refrigerant dryer first cools the air to condense moisture, then removes it from the air system. This type of dryer is used in industrial applications where ultra-dry air is unnecessary.

Pros:

• Energy Efficient: Refrigerated air dryers are generally energy-efficient and use less electricity than regenerative dryers.
• Low Maintenance: These air dryers require less maintenance, making them cost-effective in the long run.
• Reliable: Refrigerated air dryers provide a consistent dew point, sufficient for most everyday industrial air applications.

Cons:

• Not Ideal for Extremely Dry Applications: Refrigerated air dryers cannot achieve the super low dew points that regenerative dryers can.
• High Ambient Temperatures: They may struggle to deliver a consistent dew point in high ambient temperature environments because the cooling system has to work harder.
• Energy Consumption: While more energy-efficient than regenerative dryers, refrigerated dryers consume more power than membrane dryers when operating in high ambient temperatures.

The Difference Between a Non-cycling and Cycling Refrigerated Dryer

Non-cycling Refrigerated Dryers

Non-cycling refrigerated dryers are the most common type used in compressed air systems. They run continuously, ensuring a stable dew point, which is crucial for industries needing consistent air quality. However, this leads to higher energy use, especially when airflow demand is low.

Cycling Refrigerated Dryers

Cycling refrigerated dryers adjust operation based on air demand, cooling compressed air only when needed. This reduces energy costs, making them ideal for applications with fluctuating airflow. However, the dew point may vary slightly, which might not suit ultra-pure air needs.

Choosing the Right Dryer

Non-cycling dryers are reliable for consistent, dry compressed air. Cycling dryers are a smart choice for better energy efficiency and lower costs in varying conditions. Evaluate your specific needs to select the best dryer for your application.

Desiccant air Dryers

Different desiccant dryers use materials such as silica gel or activated alumina to absorb moisture. Heated desiccant air dryers use high-temperature external purge air to interact with the desiccant. They are ideal for applications in colder climates or sensitive environments requiring dry air.

Types of Desiccant Dryers

Several types of desiccant air dryers are available, with each catering to differing needs and applications. 

• Heatless Dryers: These use a small fraction of the dried compressed air to purge the off-line desiccant bed. 
• Heated Dryers: These regenerative dryers use external heat sources to regenerate the desiccant. They are more energy-efficient. 
• Heated Blower Dryers: These use a heated air stream to regenerate the desiccant, which negates the need for purging air and is ideal for high-demand applications. 

All desiccant dryers ensure quality air by effectively removing moisture and contaminants from the pressurised air that passes through them. Choosing the right type of dryer is essential for maintaining an efficient and healthy air filtration system.

Pros:

• Low Dew Point: Ideal for applications that need very dry air.
• Performance in Cold Environments: They perform well in cold environments where refrigerated dryers may struggle.
• No Dependency on Ambient Temperatures: Unaffected by high ambient temperatures, ensuring a consistent dew point.

Cons:

• High Energy Consumption: Desiccant air dryers consume more energy than refrigerated and membrane dryers.
• Frequent Maintenance: The desiccants used need replacing regularly, requiring routine maintenance.
• Cost: Higher energy consumption and maintenance requirements make desiccant dryers more costly to operate over time.

Membrane Air Dryers

Membrane air dryers are one of the four main types available in the market. Membrane air dryers use a special membrane to remove water vapour, making it ideal for low-volume air needs and outdoor or hazardous environments.

Types of Membrane Air Dryers

There are two main types of membrane dryers: non-porous and porous.

• Non-porous membrane dryers: These use a thin, dense polymer film. When compressed air enters, the film attracts water vapour in the air. The film, or membrane, selectively allows water vapour to pass through, effectively drying the air.
• Porous membrane dryers: A porous material separates water molecules from the air. As the compressed air passes through the dryer, the membrane surface adsorbs the water vapour, and dry air exits on the other side. 

Whether a non-porous or porous membrane dryer is suitable for your application depends on several factors, but mainly the required dew point and air purity. Both dryers are essential in industries where filtering the air of moisture content must be strictly controlled.

Pros:

• Energy Efficiency: Membrane air dryers consume significantly less energy compared to refrigerated or desiccant dryers, which can lower operating costs.
• Minimal Maintenance: Membrane dryers don’t require regular desiccant replacement, reducing maintenance needs and expenses.
• Stable Dew Point: These dryers are not affected by ambient temperatures, providing a consistent dew point in various operating conditions.

Cons:

• Limited Drying Capacity: Membrane air dryers may not achieve very low dew points, limiting their use in applications that need extremely dry air.
• High Initial Cost: The upfront investment for membrane dryers can be higher than for other types of dryers.

Deliquescent Air Dryers

Deliquescent air dryers use hygroscopic materials to absorb moisture from the compressed air system. They are popular in remote or hazardous locations due to their simple design and lack of electricity requirements.

Pros:

• No Electricity Needed: Deliquescent air dryers don’t require electricity.
• Easy Installation and Maintenance: These dryers have no moving parts or refrigerants.
• Cost-effective: They are typically less expensive to buy and operate than other air dryers.

Cons:

• Limited Drying Capacity: Struggle to achieve very low dew points. Unsuitable for use in applications that require extremely dry air.
• Chemical Disposal: Used desiccant tablets must be disposed of safely, which adds to their overall operating cost.
• Air Quality: There are better choices for applications that require high-quality air, as they can introduce small amounts of dissolved material into the air stream.

Air Compressors With Built-In Dryers

Some air compressors feature an integrated aftercooler in which air is cooled, a crucial component that can eliminate as much as 70% of moisture.

Pros:

• Space-Efficient: Integrated design saves space.
• Easy Installation: Fewer connections simplify setup.
• Synchronised Operation: Optimises air drying.

Cons:

• Higher Initial Cost: Combining units increases the price.
• Maintenance Challenges: Integrated units complicate servicing and repairs.
• Limited Flexibility: Custom options may be fewer.

Choosing the Right Air Compressor Dryer for Your Needs

Air dryers are designed for specific uses. So, first, you must ask yourself: why do I need an air dryer? Consider the following factors:

• Type of Dryer: There are four main different types of air dryer – refrigerant (both cycling and non-cycling), desiccant, membrane, and deliquescent. The type you choose depends on your requirements for air quality and dryness.
• Compressor Size: The size of your air compressor should match the dryer. A larger compressor might require a different kind of dryer, such as a heated desiccant air dryer.
• Industrial Application: Different industrial processes require different levels of air moisture. Some require extremely dry air, and others can manage with lesser degrees of dryness. Identify the air dryness level and amount of air your application needs before choosing a dryer.
• Air Quality: The ability of the dryer to remove moisture from compressed air is essential to consider. Dryers like refrigerant and desiccant systems efficiently extract water vapour from the incoming air, ensuring moisture-free air for your processes.

Remember, water from your compressed air can damage or adversely affect the air quality of industrial equipment. Therefore, selecting a suitable air dryer based on these factors is essential to maintaining the longevity and efficiency of your air compressor system.

Maintenance and Operational Tips

Routine Inspections

Regularly inspect your air dryer for signs of wear or leaks, focusing on key components like filters and heat exchangers. Catching minor issues early helps maintain clean, dry air and reduces long-term costs.

Replacing Consumable Parts

Replace consumable parts, such as filters and desiccants, according to manufacturer guidelines. This ensures your dryer continues to effectively remove water vapour, maintaining air quality.

Keeping the System Clean

Remove dust and debris from your compressed air equipment. Ensure that only clean, oil-free air enters the dryer to preserve its efficiency.

Monitoring Dew Point and Air Quality

Monitor the dew point to detect issues early. A rise in dew point might signal that the dryer is saturated with moisture or that the heat exchangers are not cooling the air properly.

Scheduled Maintenance

Implement a scheduled maintenance plan to check operating parameters and calibrate controls. Regular maintenance extends the life of your air-drying equipment and improves energy efficiency.

Future Trends and Innovations

The air dryer industry is not immune to innovation and technological advancement. What’s on the horizon?

• Energy-efficient air dryers will likely redefine how compressed air is cooled. Dryers come with smart cycling features that reduce power consumption without compromising compressed air quality. 
• IoT-enabled air dryers: Embedded sensors and internet connectivity mean these dryers also support predictive maintenance. The main benefits are minimal unplanned downtime and improved operational efficiency.
• Advanced portable air dryer systems: These lightweight and easily transportable air dryers are essential for supplying compressed air in remote locations or smaller workspaces.

Such technological breakthroughs could impact various industries, particularly those that require super dry air. New energy-efficient models could be a more sustainable and cost-effective solution to removing water vapour from processed air, leading to a shift in industry standards.

Let Control Gear Help You Select the Best Compressed Air Dryer

Choosing the right type of air dryer is critical and should be based on your specific requirements. Control Gear offers sustainable, efficient, and versatile solutions to remove water from your compressed air. We have a variety of dryer types to suit your needs. Whether you need clarification on whether a type of air dryer is the right fit, or need advice on how to treat air containing moisture, we’re here to help. 

Reach out to our team at Control Gear today for help – your perfect air dryer is just a call away. Contact us now to get started. 

Frequently Asked Questions about Air Compressor Dryers

What is the purpose of an air dryer for your air compressor?

The purpose of an air dryer for your air compressor is to remove water vapour within the air before it condenses into liquid, which could lead to corrosion, contamination, and damage to your compressed air equipment. This process ensures that only clean, dry air is delivered for industrial process air applications, maintaining the efficiency and longevity of your air compression system.

How do air dryers for air compressors utilise different technologies to achieve clean, dry air?

Air dryers for air compressors utilise various technologies, such as refrigerated and desiccant dryers, to achieve clean, dry air. Refrigerated dryers use heat exchangers to cool compressed air, causing moisture to condense and be removed.

On the other hand, desiccant dryers absorb moisture from the air using specialised materials, ensuring that even the most demanding industrial applications receive dry air.

How can regular maintenance of compressed air drying systems reduce the cost of ownership?

Regular maintenance of compressed air drying systems, such as inspecting and replacing consumable parts like filters and desiccants, helps maintain the air dryer’s efficiency. 

By preventing issues like wet air or moisture buildup, maintenance reduces the likelihood of costly repairs or downtime, ultimately lowering the overall cost of ownership for facilities with compressed air systems.