EXTERNAL HEAT RE - ACTIVATED (LOW PRESSURE) TYPE AIR DRYER

Low Pressure / External heat re-activated air dryers are bulky in size and the power consumption is almost double as compared to Internal Heat Re-activated Type Dryers. In capacities less than 500 Nm3/hr. these are uneconomical and not recommended. Also, since regeneration of the desiccant is by atmospheric air, these dryers give Dew Point only up to (-) 40˚C.

Characteristics

• Air capacity: 500 to 6000 Nm3/hr.
• Dew point: Up to (-)40˚C
• Operating pressure: 0.5 to 25 Kg./ Cm2g

Operating Principle

In this design there is No Loss of compressed air. Time cycle is 6+6 hours with (-) drying towers filled with Molecular Sieves & Activated Alumina. For regeneration, a centrifugal air blower and an electrical heater is provided. Desiccant is heated up to 200˚C by hot air for complete regeneration.

Process Diagram

Comparison with Internal Heat Reactivated Type Dryers

Investment cost of these Air dryers is almost double as compared to Internal Heat Re-activated Type Dryers.
It is recommended to go for this type of Dryer only when loss of compressed air during regeneration is not acceptable and Dew Point required is not critical. Also, these are recommended for capacities above 500 NM3/hr only. Operating pressure can be from 1 kg/cm2g to 50 kg/cm2g.