MMR Regenerative compressed air dryers use a desiccant to adsorb (adheres to the desiccant) the water vapor in the compressed air stream. The composition of the desiccant is not changed when in use, and the moisture is removed in the regeneration process by applying dry purge air. Regenerative desiccant dryers normally use 2 towers. One tower dries the air from the compressor while the desiccant in the other tower is being regenerated after the pressure in the tower has been reduced to atmospheric pressure.
In the heatless regenerative desiccant type, no internal or external heaters are used but the purge air requirement can range up to 18% of the total air-flow.
The typical regenerative desiccant dryer at 100 psig has a pressure dew point rating of -40°F but dew points down to -100°F can be obtained.