Mvs Engineering Limited

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 upto (-) 40˚C.

 

Characteristics:

• Air capacity: 500 to 6000 NM³/hr
• Dew point: Up to (-)40˚C
• Operating pressure: 1 to 50 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 SILICA GEL desiccant. For regeneration, a centrifugal air blower and an electrical heater is provided. Desiccant is heated upto 200˚C by hot air for complete regeneration. 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.

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 point.

 

Characteristics:

• Air capacity: 500 to 6000 NM3/hr
• Dew point: Up to (-)40˚C
  

Operating principle: Compressed air, directly from Air compressor discharge is taken to Air dryer inlet through insulated pipelines, at 120˚C(minimum) temperature. This hot air is passed through one drying vessel where saturated desiccant is regenerated by this 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.

 

Cooled to 40˚C, this air passes through the second drying vessel where moisture gets adsorbed and Dry air comes out. Cycle time is 4 hours regeneration and 4 hours drying. After 4 hours the changeover of vessels takes place automatically. In regeneration cycle heating of the bed is for 2 hours, and thereafter the bed is cooled by dry air. After bed cooling, Dry air is again cooled to 40˚C in another cooler and delivered as Dry air at 40˚C temp.

 

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 (-)40˚C Dew point for around 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.

Operating principle:

In Heatless Dryers, two vessels 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 downward through the desiccant bed in the 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 vessels changeover automatically, and Dry air is available continuously, without any surges.

• Simple Design / Easy operation: This is the simplest type of Air Dryer with Activated Alumina / Molecular sieves drying agent. This design is virtually maintenance free, fully automatic, and requires no attention for years. Heatless type dryers do not require any heating for re-generation and therefore are very simple in design and maintenance free.
  

Low Investment / 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 quick.
• Low temperature operation reduces corrosion in towers and desiccant lasts longer.
• Power requirement is 60 watts only for solenoid valves operation.
  

Heat Reactivated dryers are used when one needs compressed air of very low Dew point of (-)60˚C or (-)80˚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 points.

Characteristics:

• Air capacity: 5 to 5000 NM3/hr
• Dew point: (-)40˚C to (-)80˚C
• Operating pressure: 2 to 50 kg/ cm2g
  

Operating principle: 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 100˚C. At this temperature regeneration is complete (due to dry air purge). Dew point achieved is around (-)40˚C. If still lower Dew point is required, air purging rate is slightly increased to 5% for (-)60˚C and to 7.5% for (-)80˚C Dew point requirements.

Filters: A Pre-filter with automatic drain valve is provided to remove any physical moisture from compressed air before entering Air dryer. A micronic filter is also provided in the Dryer outlet to arrest any desiccant dust particles, up to 1 micron size. Thus, you get absolutely “Clean & dry compressed air”.

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 Heatless 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, resulting in long life of desiccant.
• Standard units are designed to deliver dry gas / air of (-)40˚C Dew Point. By using more purge airflow, and using Molecular sieves, Dew point of (-) 80˚C can be achieved.

Heat Reactivated dryers are used when one needs compressed air of very low Dew point of (-)60˚C or (-)80˚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 points.

 

Operating principle: 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 100˚C. At this temperature regeneration is complete (due to dry air purge). Dew point achieved is around (-)40˚C. If still lower Dew point is required, air purging rate is slightly increased to 5% for (-)60˚C and to 7.5% for (-)80˚C Dew point requirements.

 

Filters: A Pre-filter with automatic drain valve is provided to remove any physical moisture from compressed air before entering Air dryer. A micronic filter is also provided in the Dryer outlet to arrest any desiccant dust particles, up to 1 micron size. Thus, you get absolutely “Clean & dry compressed air”.

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 Heatless 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, resulting in long life of desiccant.
• Standard units are designed to deliver dry gas / air of (-)40˚C Dew Point. By using more purge airflow, and using Molecular sieves, Dew point of (-) 80˚C can be achieved.

For larger air drying capacities, typically above 500 NM³/hr, we supply 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 precooled with outgoing chilled air to around 25˚C and then it is cooled in a freon cooler to (+)3˚C temperature. This reduces power consumption. Outgoing dry air has (+)3˚C Pressure Dew Point and comes out at around 25˚C temperature. (+)3˚C Dew Point is equal to around (-)23˚C Atmospheric Pressure Dew Point.

Dew Point:

(-)23˚C is the best possible Dew Point achievable from Refrigerated Air Dryers. Lower Dew Point ls not possible from Refrigerated Dryer as moisture condensed would start freezing on freon tubes if lower dew points are tried. This (-)23˚C Dew point is adequate for most dry air applications and Instrument air requirements.

Characteristics:

• Air capacity: 50 to 15000 NM3/hr
• Dew point: Up to (-)23˚C
• Operating pressure: 0.5 to 100 kg/ cm2g

In small Air capacities upto 500 NM³/hr we offer Model-SP. This model features very simple and very compact design consisting of a heat exchanger with freon tubes. Air flows outside the tubes and gets cooled to 3˚C temperature. Moisture condenses out and is drained continuously. The out going air is of (+)3˚C Pressure Dew Point which is equivalent to approx (-)23˚C dew point at atmospheric pressure.