Design And Fabrication Of Prototype Internal 80k Helium Gas Purification System For Helium Plant

Cryogenics

The Helium Refrigerator/Liquefier (HRL) plant is normally operated with helium gas having purity better than 99.999 % by volume which is equivalent to having 10 PPM (parts per million) impure gas in the helium stream. In the process of gas transfer or due to some other processes before reaching to cold box of helium plant, impurity level sometimes can reach to as high as 500 PPM averaging to about 100 PPM. These impurities consist of mainly gases present in the air, hydrocarbons and H2 and traces of Ne. These gases condense at significantly higher temperature compared to the LHe temperature (4.5 K). If such high level of impurity enters the process equipment placed inside the cold box of the HRL, then it can condense and choke the pipe lines and valves leading to large pressure drop and inefficient liquefaction process. Some time, condensed and frozen impurity can destroy the blades of turbines of HRL. Hence, to be on safer side generally, internal purifiers are placed at two temperature levels (at 80 K and 20 K) inside the cold box to take care the operational problem due to impurities. Purifier at ~80 K removes Oxygen, Nitrogen and Argon from helium gas. This project is about the design and fabrication of the 80 K prototype purification system with its associated elements. Activated charcoals will be used to adsorb impure gases from cold helium gas at ~80 K and ~14 bar. The nominal flow rate of helium gas is ~120 g/s for the actual size purifier bed. Appropriate helium mass flow rate will be decided for the prototype adsorber bed. The pressure drop across the bed and filters will be measured. The break through curve or mass transfer zone (MTZ) data will be collected during this experiment and analyzed.

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