Compressed air can be dried using various methods, most commonly through adsorption drying, which involves using special materials to absorb moisture.
Understanding Compressed Air Drying
When air is compressed, its temperature rises, and it can hold more water vapor. As it cools down later in the system, this water vapor condenses into liquid water. This moisture can cause significant problems in pneumatic systems, including corrosion, damage to equipment, and contamination of products. Therefore, drying compressed air is essential for many applications.
One effective method for removing moisture is adsorption drying.
Adsorption Drying Explained
Adsorption drying utilizes hygroscopic materials – substances that readily attract and hold water molecules – to dry moist air. As compressed air passes through a bed of these materials, the water vapor is adsorbed onto the surface of the desiccant.
Common Hygroscopic Materials Used:
- Silica Gel: A porous form of silicon dioxide.
- Molecular Sieves: Materials with pores of a precise, uniform size, used for separating molecules.
- Activated Alumina: A porous form of aluminum oxide.
These materials are typically housed within equipment designed for this process.
Types of Adsorption Dryers
Adsorption dryers cycle between drying air and regenerating the desiccant material (removing the absorbed moisture) so it can be reused. Different types of adsorption dryers employ various methods for regeneration:
| Dryer Type | Regeneration Method |
|---|---|
| Adsorption Dryers (General) | Varies, often purge air or heated regeneration |
| Heated Purge Regenerated | Uses a portion of dried air, heated to regenerate |
| Blower Regenerated | Uses a blower to push ambient air, often heated |
| Heat of Compression Dryers | Utilizes the heat generated during compression itself |
These systems are chosen based on factors like required dryness level (pressure dew point), energy efficiency needs, and operational costs. By effectively removing water vapor, adsorption drying helps protect downstream equipment and processes from the harmful effects of moisture.
