Adsorption dryers are used when the compressed air application requires a pressure dew point below 0°. The regenerative desiccant dryers consist of two pressure vessels. Both vessels are filled with desiccant. One vessel is removing moisture from the compressed air.
Wet air passes directly through the desiccant bed which adsorbs the moisture. When this vessel is saturated with moisture the valves will switch and lead the air to the other standby vessel. During adsorption in the other vessel, the first vessel will be regenerated. It's a cyclic process.
The desiccant medium has a finite capacity for adsorbing moisture before it must be dried out, or regenerated. To do this, the tower containing saturated desiccant medium is depressurized and the accumulated water is driven off.
How this happens depends on the type of dryer.
- Heatless dryers use only compressed air as a purge
- Blower purge dryers use a combination of air from an external blower, heat, and minimal compressed air
- Blower zero purge dryers use a combination of air from an external blower, heat, and zero compressed air
- Heat of compression dryers use the heat of the compression
- Heated purge dryers use heat and small amount of compressed air
Depending on the technology and dew point requirement, there is always the best choice of desiccant, sometimes a combination of multiple layers of desiccants used in our designs. In this way, we will ensure required PDP levels and maximized lifetime for desiccant.
The rotary drum dryer also uses adsorption technology. The desiccant does not come in granular form. Instead, it is bonded with a binding material in a honeycomb structure. The main advantages are:
- No erosion of desiccant beads
- No escape of beads
This unique technology does not require any additional energy, as it is using the heat of compression. The rotating drum is divided into sections. In general 3/4 of the drum is used for adsorption, while 1/4 is used for regeneration. It's a continuous process as the drum rotates and therefore doesn't require any switching valves.