Although there are other less common types of adsorption dryers, they are not discussed in this article. All typical adsorption dryers have two pressure vessels filled with desiccant particles and a valve control system that directs compressed air from one pressure vessel to another. The ability of desiccant particles to remove water vapor (adsorption) in compressed air before saturation is limited. Once the desiccant is saturated, the moisture in the desiccant must be removed in the regeneration cycle, otherwise the dryer will not be able to absorb the moisture in the air and reduce the dew point of compressed air to a lower level.
Before the desiccant in one pressure vessel is saturated, the valve control system will deliver the compressed air which is not completely dry to another pressure vessel filled with desiccant. At the same time, put the former pressure vessel under atmospheric pressure, pass in the dried compressed air, take away the moisture in the saturated desiccant, and regenerate the desiccant. Because compressed air at atmospheric pressure, dew point will be reduced, so its ability to take away water is stronger. The desiccant in the two pressure vessels is alternately dried and regenerated like this, and the cycle is usually 10 minutes. The compressed air consumed in this recycling process is about 15% to 20% of the rated output of the dryer.
It should be noted that 15% ～ 20% here is 15% ～ 20% of the rated output of the dryer. In some cases, the dryer will not be fully loaded. For example, when the dryer is working at half load, the compressed air used to remove moisture from the desiccant will be 30% to 40% of the output. In the process of drying air, this kind of dryer itself will use up most of the compressed air that has been dried, which is also the reason why auditors are not optimistic about this kind of compressor.
In order to make up for this shortcoming, designers have proposed different versions of adsorption dryer, one of which is the method of thermal regeneration adsorption drying. Similar to the heatless regenerative adsorption dryer, the saturated desiccant still needs to be dried with the dried compressed air, but the compressed air will be heated by the electric heater before it is introduced into the pressure vessel.
This design change results in less compressed air consumption, which is about 7.5% of the rated output of the dryer. It can release more compressed air to meet the demand and reduce the overall electrical operation cost. This type of dryer is slightly larger than the heatless regenerative dryer, and the cycle is changed to 4 hours.