We are using this type of air compressor.
Screw type air compressor
Rotary screw air compressor operation principle
YoutubeA rotary screw compressors use two helical screws, known as rotors, to compress the gas. In a dry running rotary screw compressor, timing gears ensure that the male and female rotors maintain precise alignment. In an oil-flooded rotary screw compressor, lubricating oil bridges the space between the rotors, both providing a hydraulic seal and transferring mechanical energy between the driving and driven rotor.
Gas enters at the suction side and moves through the threads as the screws rotate. Clearances between the threads decrease and compress the gas. The gas exits at the end of the screws. (from wikipedia)
From the view of control circuit, air compressor using star-delta starter for the main motor (for compressor) and It operates with its pre-determined pressure (we are using 7.4bar for plant main air compressor, and the other for ash handling system setted at 6.5 or 7 bar). for the industrial applications, air compressor need load/unload function for its continuous air consumption over the whole plant instrument and other consumptions.
Air dryer There are several types of air dryer, and we are using Heatless type and refrigerated type
Heatless Type Air / Gas Dryers.The working principle of heatless air dryer is based on “Pressure swing absorption” and the operation is fully automatic & simple. The moisture from compressed air/gas is removed by absorption. Two drying towers are provided that keep on changing their position according to the designed cycle. While in one chamber drying of air is in operation, the other gets re-generated by de-pressurization and using a small portion of the dried air. This dried air flushes out the moisture from the absorption media, absorbed in previous cycle. Slide piston valve, pneumatic diaphragm operated exhaust valves are provided for complete automatic change over. Moisture level 80 ppm(dew point - 40 degree C) or less can be achieved. The dryer is very compact and very easy for operation and maintenance.
Heat regenerated type dryerIn these air dryers, external heat used for regeneration of the absorbent. and various dryers that are classified as under
- Internal heaters type : The electric heaters are embedded in the drying towers which heat up absorption media upto required degree and the absorbed moisture is then flushed out with the help of a very small amount of dried air / gas.
- Blower heat regenerated ; In blower heat regenerated dryer, we can save compressed air which is to be washed in regeneration. A blower provides the atmospheric air which is heated in an external heater and is passed throuth the drying tower from where it takes away all the moisture.
- No purge loss split flow type : The wet compressed air/gas is split at the inlet through differential valve. Part of the stream is passed through an external heater and then the tower regeneration where it carries the absorbed moisture and then passed through a cooler where the absorbed moisture is condensed and separator.
- Heat of compression type : In heat of compression dryer, hot compressed air from compressor is directly passed through the drying tower to be regenerated and hence the use of heater is eliminated. However, a small capacity electric heater is provided in the incoming hot air line which takes care of the lower temperature of the hot air due to any reason. There is considerable power saving in this type of dryer and dew point upto -50 degree C. can be achieved.
--> we are not using this type of dryer
Refrigerated type Air DryerRefrigerated air dryer is the most commonly used compressed air dryer for most industrial applications. It is extensively used for the drying of plant air and other utility gases like hydrogen gas, nitrogen drying etc. In this type of dryers the moisture present in the compressed air / gas is condensed by chilling it down from 0 degree C to 4 degree C(?) by using effective refrigeration cycle and the condensed moistures is separated by efficients filters. The dew point is 23 degree C (at atmospheric pressure) but the running cost is very low. A full range of air-cooled as well as water cooled refrigerant air dryers are available for moisture removal & to provide dry clean air to any size and type of compressed air & pneumatic systems.
you can see the gray panel rear side of the air compressor, this is refrigerated air dryer.
