Heatless twin-tower regenerative dryers consist of two identical tanks (towers) filled with desiccant. The moist compressed air enters the bottom of the active tower and moisture within the compressed air adsorbs onto the surface of the desiccant.
Desiccant dryers remove water from compressed air by adsorbing it onto the surface of the desiccant. Desiccants, usually silica gel, activated alumina, or molecular sieve do not chemically react with the water.
Activated alumina is highly porous aluminum oxide and has a very large surface area for its size (350 sq. meters/gram). Its smooth uniform ball-shape prevents channeling of the airflow, which maintains low bed velocities and increases air contact time for efficient moisture removal and minimal pressure drop.
Heatless Twin-Tower Regenerative Dryers
Heatless twin-tower regenerative dryers consist of two identical tanks (towers) filled with desiccant. The moist compressed air enters the bottom of the active tower and moisture within the compressed air adsorbs onto the surface of the desiccant. The second tower’s desiccant is re-activated (dried) by directing about 20% of the dry compressed air output back through the inactive tank. After a set period of time, the flow through the towers is reversed.
Heatless twin-tower heatless regenerative dryers usually produce a dew point of -40ºF and can optionally be as low as -100ºF.
Heatless regenerative dryers can be completely controlled with pneumatic signals, they can be used in hazardous areas.
Heated Twin-Tower Regenerative Dryers
Heated twin-tower regenerative dryers function the same as heatless regenerative dryers. The only difference is that once the active tower’s desiccant becomes saturated, the desiccant is heated to dry it.
The heat can be supplied by elements embedded in the tower, or a heated jacket wrapped around the tower.
Dry compressed air is still used to purge the drying tank, but only about 3-8% of the dryer output is used to carry away the moisture.
Heated twin-tower regenerative dryers usually produce a dew point of -40ºF, but can be set-up to operate with a dew point of -100ºF.
Blower Purge Twin-Tower Regenerative Dryers
Blower purge twin-tower regenerative dryers are similar in concept to the heatless regenerative dryers except no purge air is redirected into the drying tank.
Instead, a separate blower supplies heated air from the surrounding environment to the drying tank.
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