A desiccant compressed air dryer makes use of a special material, called desiccant to parch the compressed air. The desiccant is made from a material that, for lack of a better term, ‘likes’ water. The water attaches itself to the surface of the desiccant and from time to time, the desiccant has to be dried, or ‘regenerated’, in order to remove the water again.
In order to have the largest possible surface, the desiccant is utilised in the form of thousands of tiny beads. The types of desiccant that are commonly used are silica gel and activated alumina.
How does desiccant compressed air dryer work?
A desiccant dryer typically has two similar towers, filled with desiccant. While one tower is used to dry the compressed air, the other tower is regenerated.
Every now and again — controlled by a central control unit — the dryer changes towers. The compressed air is then dried by the second tower and the first tower, filled with wet, saturated desiccant, is then dried.
In most dryers, there is a small glass and behind the glass, you can see small beads. These beads are not the drying-desiccant, but rather an indicator. Its colour will change when the air is too moist. It needs to be checked every so often to ensure that the dryer is functioning properly.
The regeneration or drying of the desiccant
When the desiccant has completed its job after some time, it will absorb all the water from the compressed air and is then saturated with water. It will not be able to hold any more water. In order to recycle the desiccant, you will need to discard all the leftover water. This is called regeneration.
The regeneration process is done within one of the air dryer towers, the one that is not active. There are two techniques of regenerating the desiccant: by using hot air or by using dried compressed air.
In the hot air method, a separate system involving a fan with an electrical heater is used to push the hot air through the desiccant in order to dry it. This is just normal air extracted from the compressor room.
There are also specialised dryers available for use with screw compressors that are free of oil, which used the heat from the compressor to regenerate the desiccant (and consequently saving energy and money). This kind of dryer consists of a rotating drum. One-quarter of the air is regenerated, while the rest is drying the compressed air.
A third method of drying the desiccant is by using dry, compressed air. This method is typically used in the smaller dryers and is generally not suitable for the bigger dryers. With this method, a part of the compressed air that has been dried is used to regenerate the desiccant. This means that even less compressed air is made available for your tools and machinery.
Nasta Compressed Air Services is a company, founded back in in 1994 by Mr. Jan de Jong, operates from Alberton, Johannesburg Gauteng with over 27 years’ experience in the compressor industry. Nasta Compressed Air Services is fully equipped to deal with any kind of service, repairs or refurbishment on any compressor. So, though one might know how to operate the machinery, the servicing and repairing of the machinery is Nasta’s area of expertise.