Heatless Type Air Dryer.
In Heatless Dryers, two vessel filled with desiccant are provided which cycle automatically, producing dry air continuously. In these units, wet air enters the bottom of one Vessel and passes upwards through the desiccant bed where the moisture is adsorbed. The dry air comes out from the top. A small portion of dry air is passed downwards through the desiccant bed in second vessel, which is under re-generation. Moisture laden purge air is then vented out to atmosphere.
The purge loss is around 7.5% of the total air flow. At preset interval, the vessel changeover automatically, and Dry air is available continuously, without any surge.
This is simplest type of air dryer with Activated Alumina / Molecular Sieves drying agent. This is virtually maintenance free, fully automatic, and requires no attention for year heatless type dryers do not require any heating for re-generation and therefore are very simple in design and maintenance free.
Low Operating Cost:
· Due to its inherent simple design, investment in this type of dryer is the cheapest and the payback on this investment is very quickly.
· Low Temperature operation reduces corrosion in tower and desiccant lasts longer.
· Power requirement is 60 watt only for Solenoids Valves Operation.
· Air Capacity: 5 to 10000 NM3/Hr.
· Dew Point : Up to (-) 60°C
· Operating Pressure: 5 to 35 Kg/cm2g
Heat of Compression / HOC Type Air Dryer.
HOC type dryer has NIL operating cost in this design hot air coming out from Air compressor discharge is used for regeneration of desiccant and so no external electric regeneration heating is required. This design easily produces dry air of (-) 40° C Dew Poin.t
Air Capacity: 500 to 5000 NM3/hr.
Dew Point : Up to (-) 40°C
The Heat of Compression dryers (HOC) are the latest generation chemical dryers based on adsorption principle. It does not have complex valuing & is eliminated with purge loss drawback as in heatless type dryer.
The hot air from the Compressor at 120°C and higher temp. is used directly for regeneration of the desiccant. After regeneration, this air is cooled down to 40°C and then it is dried in second tower. Thus, the use of heaters is eliminated. For e.g. in the 6+6 Hrs. Cycle the hot air is fed for regeneration for 4 Hrs. and for balance 2 Hr. a changeover takes place where the air is first
Cooled in cooler, then dried and before going to the outlet, cools the regenerated desiccant bed, thus bringing it down to ambient temperature. This cycle is reversed for the next 4Hrs. where the Absorber drying the air in the previous cycle goes for regeneration and vice versa.
Mass quantity instrument, process air in chemical industries & other engineering applications where mass volume air may be required.
Internal Heat Re – activated type.
Heat Reactivated Air Dryer is used when one needs compressed air of very low dew point of (-) 60o C or 80oC. In Heat Reactivated Air Dryer, 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 points.
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 regenerates 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 degree c. At this temperature, regeneration is complete (due to dry air purge). Dew point achieved is around 40 degree c. If still lower dew point is required, air-purging rate is slightly increased to 5% for 60 degree C and to 7.5% for 80 degree C DEW point requirements.
A pre-filter with automatics drain valve is provided to remove any physical moisture from Compressed air before entering air Dryer. A Micron filter is also provided in dryer outlet to arrest any desiccant dust particles, up to 1 micron size. Thus you get absolutely “Clean & dry compressed air.
· Air Capacity: 500 to 5000 Nm3/Hr.
· Dew Point : Up to (-) 40°C
· Operating Pressure: 5 to 35 Kg/cm2g
In this design there is no loss of compressed air time cycle is 6+6 Hrs with (-) drying towers filled with silica gel desiccant for regeneration , a centrifugal air blower and an electrical heater is provided desiccant is heated up to 200°C by hot air of completely re –generation
Compression with internal heat re-activated type air dryer:
· Investment cost of these Air dryer is all most double as compared to internal heat re-activated air dryers.
· It is recommended to go for this type of dryer only when loss compressed air during regeneration is not acceptable and dew point required is not critical also these are recommended for capacities above 500Nm3/hr only. Operating pressure can be from 1 to 50 kg/cm2g.