All atmospheric air contains water vapor, but as air is being compressed, the relative humidity of water increases to 100%. To avoid problems caused by water precipitation in pipes and connected downstream equipment, compressed air must be dried.
Here are some methods for drying compressed air:
Air is compressed to a higher pressure than the intended working pressure, which means that more water is condensed out of the system during the compression process. Additional water is separated out as the air is cooled in the compressor aftercooler. The air is then allowed to expand to the working pressure, and a lower pressure dewpoint is attained. This method is only suitable for very small air flow rates due to its high energy consumption.
The refrigerant drying process involves cooling the compressed air to allow a large amount of water to condense and separate. After cooling and condensing, the compressed air is reheated to room temperature so condensation does not form on the outside of the pipe system.
The working principle of adsorption dryers is simple – moist air flows over desiccant materials to dry. Once the desiccant material is absorbed with water, it is regenerated to regain its drying capacity. Adsorption dryers are typically built with two drying vessels with the first vessel drying the incoming compressed air while the second vessels is regenerated.