Heat regeneration adsorption air dryers are used when one needs compressed air of very low Dew point of (-)60oC or (-)80o Deg C. In this design, the desiccant is regenerated at higher temperature, along with small quantity of Dry air purge. Due to purging with Dry air and thermal regeneration, residual moisture loading on desiccant becomes low and this gives very low Dew point. The Drying unit has 2-vessels filled with Activated Alumina or Molecular sieves desiccant. One vessel remains in drying cycle for 4 hours, while other vessel is simultaneously regenerated at atmospheric pressure. Around 3% flow of dryer capacity is used as purge for regeneration. Electrical heaters are provided in a central finned Stainless steel pipe in both drying vessels. Heating cycle is for 2 hours and in this time hot purge air increases desiccant temperature to around 100oC. At this temperature regeneration is complete (due to dry air purge). Dew point achieved is around (-)40oC. If still lower Dew point is required, air purging rate is slightly increased to 5% for (-)60oC and to 7.5% for (-)80oC Dew point.