DU Digital Processes Pvt., Ltd.

DU Digital Processes Pvt., Ltd.

Air Drying Unit


When atmospheric air burns in the presence of Sulphur inside the furnace of the FilmType Sulphur Burner the moisture contained in this air gets converted into Sulphurus acid (H2SO3). This acid corrodes the walls of the scrubbers and coolers of the FilmType Sulphur Burner, and drastically reduces their life. The Air Drying Unit developed by Digital Utilities is a very valuable adjunct to the FilmType Sulphur Burner and serves to cool the atmospheric air entering into the FilmType Sulphur Burner to about 40°C to 50°C, so that this air becomes dry and looses its moisture.

Atmospheric air at ambient temperature (varying as per different location & seasons) is passed through a chilled water scrubber where the temperature of air is brought down to desired level of around 5°C ± 2o C, thereby condensing the moisture. The air leaving the chilled water scrubber has a dew point of less than 5°C. The water chiller has Freon running in a closed loop as cooling medium. Freon compressor compresses Freon vapors from freon - water heat exchanger (chiller), which are subsequently cooled in a condenser. The liquid Freon then passes through filter/dryer and then through an expansion valve to the Freon- water heat exchanger. For safe & smooth operation of the chiller, necessary instruments have been provided.

The unit is installed on the suction side of the air compressor and is designed to cool the air to 5°C. It comprises mainly of the following.

Water chilling Unit, complete with:

  • Expansion valve
  • Water – Air scrubber (Direct air cooler)
  • Freon compressor
  • Water cooled condenser
  • Freon filter
  • Instrumentation for automatic operation
  • Hot gas by pass valve

This is a direct expansion type cooling system in which water comes in direct contact with cold Freon finned copper tubes so that its temperature is lowered down to 5°C. The cooling effect is due to expansion & evaporation of Freon. Vapor Freon leaving the chiller is compressed and cooled in the condenser. Freon condenser is water-cooled. Enough water should flow through it so that the Freon compressor discharge pressure is not more than 250 psig. The cooling water coming out of the condenser should not be more than 35°C, if it is more, than water flow rate should be increased for more efficient heat transfer to take place.

The liquid Freon from condenser passes through the filter / dryer and to the expansion valve. The Freon gas again goes to condenser through compressor.  Thus Freon flows in closed loop. 

Direct Contact Cooler

Atmospheric air is impinged on chilled water which is pumped in a closed loop in a specially designed Direct Contact Cooler to reduce its temperature to below 50°C± 20°C, thereby condensing its moisture. The pH of the warm water emerging from the direct contact cooler is monitored periodically to give an indication of the SO2 in the ambient air. In case of any decrease in pH, this water is changed.

Electrical / control Panel

The On / OFF operation of Freon compressors is controlled through the control panel.  Temperature controller has been provided at the outlet of the dryer to maintain the outlet temp of the air. For safety of Freon compressor, LP/HP cut–out is also provided. Overload relay on the compressor starter is for the safety of the electrical drive. Indicating lamps for ON/OFF conditions are also provided.

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