Desiccant Air Drying Technologies
Twin Tower Heatless Desiccant Dryers
The CompAir AX-Series uses twin desiccant towers and strategically positioned valves to dry the compressed air.
The compressed air produced is thoroughly dried as it is directed through the on-line desiccant-filled tower of the dryer. As the desiccant in this tower adsorbs moisture from the air, the desiccant in the dryer’s offline tower is purged of moisture and readied for use.
Advantages at a glance:
High Reliability - proven technology used in thousands of applications and installations worldwide.
Low Capital Investment - large range, available for precise sizing to suit your needs.
High Air Quality - pre and post filter included, helping you to meet stringent air quality requirements.
Energy Efficient - with the optional high efficiency Energy Management System (EMS) offers even greater efficiency.
Standard features include:
High Efficiency Pre Filter and Dust Filters
IP54 electrical enclosure
Digital controller
Tower pressure gauges
Colour change moisture indicator
Optional features include:
Energy Management System (EMS) with dew point display
Fail-to-Shift alarm - Monitors the dryer sequencing functions to ensure proper dryer operation by sensing the pressure in each tower, sending an alarm in case of anomalies. This option is available from models 1000m3/h and above
IP65 electrical rating plus stainless steel control box
4-20 mA signal (requires EMS) is available should you need to get 4-20mA to your SCADA system
Different tower vessels design code
Stainless steel control air tubing
Filter monitoring - Differential pressure switches installed on filter monitor performance. Display options include analog and digital
-70˚C pressure dew point
No air loss drain for filters with alarm
Marine paint
The above diagram shows how the heatless dryer diverts a portion of the dried compressed air to the off-line tower. This dry air then flows through and regenerates the desiccant. The purge air, now moisture laden, is harmlessly exhausted through a muffler to the atmosphere. This technology requires a small portion of the dried compressed air to be diverted from the air system for desiccant regeneration.
Twin tower heatless desiccant dryers—like the CompAir AX-Series you mentioned—are a widely used technology for achieving very low moisture levels in compressed air systems. Here’s a clear breakdown of how they work and why they’re used:
🔧 How Twin Tower Heatless Desiccant Dryers Work
These systems use two towers filled with desiccant material (such as activated alumina or silica gel):
1. Drying Phase (Adsorption)
Compressed air flows through one tower.
The desiccant inside adsorbs moisture from the air.
Dry air exits the system with a very low dew point (often down to -40°C or lower).
2. Regeneration Phase (Heatless)
The second tower is being regenerated at the same time.
A small portion of the already dried air (called purge air) is expanded and passed through the saturated tower.
This purge air removes the trapped moisture from the desiccant.
No external heat is used—hence “heatless.”
3. Switching Cycle
After a set time, valves switch:
The regenerated tower becomes the drying tower.
The saturated tower goes into regeneration.
This cycle repeats continuously.
⚙️ Key Features of CompAir AX-Series
Twin tower design ensures continuous operation.
Strategically positioned valves manage airflow and switching cycles.
Heatless regeneration simplifies design and reduces maintenance.
Capable of achieving very low pressure dew points (e.g., -20°C to -40°C or lower).
👍 Advantages
Simple and reliable operation (no heaters or blowers).
Low maintenance compared to heated dryers.
Ideal for applications needing ultra-dry air (instrumentation, pharmaceuticals, food processing).
⚠️ Considerations
Uses purge air (~10–15%), which reduces overall system efficiency.
Not as energy-efficient as heated or blower purge dryers for large systems.
Requires proper filtration to protect the desiccant.
📌 Typical Applications
Instrument air systems
Pharmaceutical manufacturing
Food & beverage processing
Electronics and semiconductor industries
