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LIQUID RING COMPRESSOR SYSTEM PRINCIPLE

LIQUID RING PRINCIPLE:Liquid ring compressors belong to the positive displacement compressor family. Ascompression element, instead of a metallic piston, they use a liquid that is centrifuged ina casing with a specific shape. The liquid can be water, sulphuric acid, crude oil, gasolineor any other liquid that does not react with the gas that has to be compressed.

This specific feature allows to reduce the wear of the metallic parts theoretically to zeroand therefore to maintain their efficiency for an extremely long time. In fact, the only

wear parts are the mechanical seal and the bearings. In other types of positivedisplacement compressors also the parts that realize the compression are wear parts andtherefore their efficiency will decrease continuously in a short time. Consequently, theyrequire high maintenance costs to keep their efficiency continuously at an acceptablelevel.

THE WORKING PRINCIPLE OF A LIQUID RING COMPRESSOR:

In a liquid ring compressor the casing is filled with the liquid that is called seal liquid up

to the rotor centerline. The process gas enters the compressor through its conicaldistributor that is fixed to the compressor front cover. During compressor start up the

seal liquid will be centrifuged by the impeller rotation along the inner wall of the casingthat has a double eccentricity shape. The conical distributor has two suction ports andtwo discharge ports, each of them opposite to the other. During the first quarter ofturning, the gas is sucked to both suction chambers of the casing. During the second

quarter of turning the gas is first compressed and then pushed out through the twodischarge ports. During the third and the fourth quarter of turning the cycle is repeated.In this way for each complete turning of the impeller, the gas is sucked, compressed and

pushed out twice. The radial forces originated, due to the gas compression, are thereforeperfectly balanced. The unit control system is designed by manufacturer and allowsreliable and safe operation of the compressor. Utilities, seal flushing and make up

systems are defined at the design stage of the liquid ring compression unit.

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WORKING PRINCIPLE OF A LIQUID RING COMPRESSION SYSTEM:

PHASE 1: The process gas and the seal liquid enter the compressor through the conicaldistributor.

PHASE 2: after the compression the process gas and the seal liquid leave thecompressor and both enter the separator tank.

PHASE 3: the seal liquid is separated form the process gas by means of gravity andpushed back to the compressor by means of the pressure differential existing betweenthe separator and the suction chamber of the compressor. Before entering again thecompressor, the seal liquid flows through a cooler, called seal liquid cooler to reduceits temperature to the initial value (isothermal compression).

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GASES AND SERVICE LIQUIDS:

Gas handled by compressors SERVICE LIQUIDBF3 (boron fluoride) XylolsBlow down gases (mix HC) Water / Gasoline / Amine

Mix HC (refinery units) Water / Gasoline / Amine

CH4 Water

CO2 Water

Dry chlorine Sulphuric acid

EDC EDC

Ethylene Acetic acid

H2 Water / Solvent

H2S Water / Amine

HCl Sulphuric acid

NOx Nitric acid + water

Olefins (propylene ethylene recovery) Water

VCM Water

Vent gas EDC / Water

Wet chlorine Water