What is a Desiccant Compressed Air Dryer?
A desiccant compressed air dryer is an effective way to remove all water from your compressed air. It works by the use of a special material called desiccant. This material is made of a material that loves water, and whenever it comes into contact with it, water sticks to the desiccant surface. In order to maintain effectiveness, desiccant required regeneration through drying on a regular basis. This will remove the water from the surface and leave it seeking new water to stick to when you restart the air dryer.
The desiccant is applied in the form of small beads. When put together in the thousands, these beads can cover a large surface space and be used to attract larger quantities of water. How does it work within an air dryer?
A desiccant air dryer will traditionally be made up of two towers filled with desiccant. The one tower is used to attract water and dry the compressed air, whilst the other tower (which is identical in how it is built) will be used to regenerate desiccant. From time to time a central control will switch between the two towers, with the reverse application now required. The first tower will dry the saturated, wet, desiccant, and the other tower will begin to dry the compressed air.
This is a simple process, and on the majority of desiccant air dryer towers there will be a small section of glass to provide a view of the tower interior. Small beads behind the glass are an indicator as to whether the air is at too high a level of water saturation and they will change colour if this is the case.
Once the desiccant has absorbed as much water as it can from the compressed air, and is fully saturated the regeneration process must begin. As previously discussed, in the two-tower system, one tower is used for this regeneration process. There are two ways in which this occurs. The first is through hot air, with an electric heater and fan (separate to the tower system) is used to blow hot air through the desiccant until it is dry.
Dry compressed air can also be used to dry the desiccant, especially in smaller air dryers. Part of the recently dried compressed air is used to dry the saturated desiccant. Another process involved special dryers that use oil-free screw compressors. These take the heat from the compressor and use that to regenerate the desiccant.
The installation process for a desiccant air dryer is simple as long as you follow some simple rules. To install correctly will help you to maintain a cost effective air compressor for many years.
A filter should be used to ensure that no air that is entering the dryer has water or oil drops present. A moisture-trap, water-filter and oil-filter can all be used to clean up the air before it enters the dryer. If you do not do this, the desiccant will not be able to soak up water from the compressed air, as it will already be saturated with oil and water. Once installed an after-filter can be used to pick up dust, protecting the equipment and helping with maintenance.