Compressed Air Dryers
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
Here’s a clear, structured explanation of your three topics—moving from general to specific so you can understand how they connect in real industrial systems.
1. Compressed Air Dryers
A compressed air dryer removes moisture (water vapor) from compressed air to prevent:
Corrosion in pipelines
Damage to pneumatic tools
Product contamination
Why drying is needed
When air is compressed, its temperature rises and moisture becomes concentrated. If not removed, it condenses later in pipelines and equipment.
Common Types
Refrigerated dryers → economical, moderate dryness (~+3°C dew point)
Desiccant dryers → very dry air (down to –40°C or lower)
Membrane dryers → compact, niche use
👉 In critical industries (pharma, electronics, painting), desiccant dryers are preferred because they achieve ultra-low moisture levels.
2. Desiccant Air Drying Technologies
These systems use adsorption (moisture sticks to a solid surface) instead of cooling.
How it works
Wet compressed air passes through a desiccant bed (e.g., activated alumina, silica gel)
Moisture is trapped on the surface
Dry air exits the system
The desiccant must then be regenerated for reuse
Main Technologies
1. Heatless (PSA – Pressure Swing Adsorption)
Uses dry compressed air for regeneration
No external heater
Simple and widely used
2. Heated Desiccant Dryers
Use external heaters
Lower air loss
Better energy efficiency
3. Blower Purge Dryers
Use ambient air + heater
Minimal compressed air loss
Ideal for large systems
👉 All of these rely on two alternating chambers (towers) for continuous operation.
3. Twin Tower Heatless Desiccant Dryers
This is the most common industrial desiccant dryer design, especially in small to medium plants.
Core Concept
A twin tower system has:
Tower A → Drying (adsorption)
Tower B → Regeneration (desorption)
They switch automatically to ensure continuous dry air supply.
Working Principle (Step-by-Step)
1. Adsorption (Drying Phase)
Moist air enters Tower A
Desiccant adsorbs water vapor
Dry air exits (typically up to –40°C dew point)
2. Regeneration (Heatless Process)
A portion (~10–15%) of dry air is diverted
This air expands to low pressure
It flows through Tower B to remove moisture
3. Switching Cycle
After a fixed time (5–10 min typical)
Towers switch roles automatically
Continuous operation is maintained
Key Characteristics
✔ Advantages
Simple design (no heaters)
Reliable and low maintenance
Suitable for remote or hazardous areas
Consistent low dew point (-40°C or better)
❌ Limitations
Uses purge air (≈15–20%), reducing efficiency
Higher operating cost due to air loss
Typical Components
Two pressure vessels (towers)
Desiccant material
Switching valves & controller
Pre-filters and after-filters
Purge exhaust system
Applications
Pharmaceutical manufacturing
Food & beverage processing
Electronics & instrumentation
Paint spraying / powder coating
Industrial automation systems
Quick Comparison
Feature Desiccant Dryer Twin Tower Heatless Dryer
Technology Adsorption Adsorption (PSA)
Towers Usually dual Always dual
Regeneration Heat / air / blower Only purge air
