To get compressed air of very low Dew point of (-)60^oC or (-)80⁰ C then heat reactivated dryers are used. In our range of Internal Heat Re-activated Dryers design, the desiccant is regenerated at higher temperature 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 regenerate 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 100^oC. At this temperature regeneration is complete. Dew point achieved is around (-)40^oC. Whenever lower dew point is required, air purging rate is slightly increased to 5% for (-)60^oC and to 7.5% for (-)80^oC dew point.

Filters
A Pre-filter with automatic drain valve is used to remove physical moisture from compressed air before entering air dryer. A micronic filter is also used in the dryer outlet to arrest any desiccant dust particles, up to 1 micron size. It provides clean & dry compressed air.

Salient Features

• A fully Automatic unit requiring no attention of the operator. Heaters switch on/ off and all valves operate automatically.
• Pressure is equalized to line pressure before changeover of drying vessels. This prevents pressure and flow surge, and, desiccant dusting
• Low purge air requirement in comparison to heat less type dryer.
• Desiccant life is around 5 years.
• Internal heaters provide maximum heat transfer efficiency resulting in lower power requirement.
• Counter current heated dry purge air provides maximum removal of moisture with minimum gas purge loss.
• Heaters are not in physical contact with the desiccant.
• Standard units are designed to deliver dry gas / air of (-)40⁰C dew point. By using more purge airflow, and using molecular sieves, dew point of (-) 80⁰C can be achieved.

Air capacity : 5 to 5000 NM3/ Hr.
Dew point : (-)40^oC to (-)80^oC.
Operating pressure : 2 to 50 kg/ cm2g.

Compressed Hot air, directly from air compressor discharge is taken to air dryer inlet through insulated pipelines, at 120^oC(minimum) temperature. This hot air is passed through drying vessel, where saturated desiccant is regenerated by hot air. After picking up moisture from desiccant bed, the air is cooled in an intermediate cooler.

Here moisture is condensed and removed by auto drain valve. After the air is cooled to 40^oC, then it passes through the second drying vessel where balance moisture gets adsorbed and Dry air comes out. The cycle time is 4 hours regeneration & 4 hours drying.

After 4 hours the changeover of vessels takes place automatically. In regeneration cycle heating of the bed is only 2 hours and thereafter the bed is cooled by dry air. After bed cooling, the dry air is again cooled to 40^oC in another cooler. The air is delivered out of the unit at 40^oC temp.

This dryer is fully automatic with pneumatically actuated ball/ plug valves. A sequence timer control operates these valves. Desiccant used activates alumina and dries the air upto (-)40^oC Dew point.

Salient Features

• No power requirement for regeneration.
• No loss of compressed air.
• Maintenance is easy as there are no Blower, no Heaters and no moving parts.
• Maintains desiccant adsorption capacity to give (-)40⁰C Dew point for almost 5 years.
• Low-pressure drop across the Dryer- less than 0.3kg/cm2.
• Skid mounted construction on channel base frame.
• Fully Automatic, continuous operation.
• Negligible operating cost. It neither requires Electric power for regeneration, nor there is any loss of compressed air

Air capacity :500 to 6000 NM3/Hr.
Dew point : up to (-)40^oC.

In small Air capacities upto 500 NM3/hr we offer Model-SP. It's simple and compact design consisting of a cylindrical heat exchanger with freon tubes. Air flows outside the tubes and gets cooled to 3°C temperature.

The moisture condenses out and is drained continuously. The out going air is at 3°C temperature with (+) 3°C pressure dew point. It is equivalent to approx (-) 23°C dew point of atmospheric pressure.

For larger Ah capacities, above 500 NM3/hr, we recommend Model - AA. It is a skid mounted unit consisting of Air-Freon chiller, air to air pre-Cooler and a moisture separator.

First air is pre cooled with outgoing chilled air to around 25°C and then it is cooled in a freon cooler to {+) 3°C temperature. This reduces refrigeration load of the unit. Outgoing dry air has (+) 3°C pressure dew point and comes out at around 23°C dew point of atmospheric pressure.

(+) 3°C dew point in refrigerated air dryer corresponds to around (-) 23°C atmospheric pressure dew point. If lower than this dew point is required then that is not possible from refrigerated dryer, as the moisture condensed would start freezing on freon tubes after this stage. (-) 23°C is the best possible dew point achievable from refrigerated air dryers.

Capacities : 5 to 15000 NM3 / hr
Pressure : 0,5 to 100 kg/cm2g
Dew Point : Upto (-) 23°C