General process description
The liquefier is a fully automated, processor-controlled refrigeration system with a screw compressor, expansion turbines and an integrated purifier for processing contaminated helium (He).
Features & Benefits
- Universal application (liquefier, refrigerator, radiation shield cooling)
- Simple operation
- Fully automated operation
- Automated purifier without external cooling
- Modular, compact design
- Extremely quiet and vibration-free
- No special fastenings or foundations required
- Optional – performance increase through LN2 pre-cooling
The cooling process
The cooling takes place after the Claude process.
A screw compressor compresses purified helium from 1.05 to approx. 12.5 bar, constantly dissipating the resulting compression heat. Traces of oil in the circulating gas are removed by coalescer filters and a special oil absorber.
The actual refrigeration is generated by two dynamic gas-bearing expansion turbines connected in series, whereby part of the circulating gas is expanded while performing its work. In stationary operation, the final temperature after the second turbine is approx. 12 K.
At temperatures below 8 K, part of the circulating gas is expanded to approx. 1.3 bar by a Joule-Thomson valve (JT). This produces partly liquid helium with a temperature of approx. 4.5 K. In the transfer line, the 4.5 K cold helium is transported from the Joule-Thomson valve to the liquid helium dewar.
The cold helium gas produced during the expansion process is used together with the low-pressure flow from the turbines in a counterflow principle to cool the warm gas and is circulated continuously. Aluminium plate fin heat exchangers are used for this purpose.
In order to avoid deposits caused by frozen impurities in the process, only high purity helium may be used in the liquefaction circuit. However, helium, which is fed
into the recovery process, is contaminated with air, nitrogen or other gases. The diffusion of air in different components (gas bag / gasometer) also has a negative
effect on the gas quality. In helium liquefiers, integrated cleaning lines that use the coldness from the process gas are usually aimed at. This has the advantage that no additional equipment such as LN2 is required. In addition, the contaminated helium can be cooled down to approx. 30 K in order to freeze out residual contamination.
Standard scope of supply
- Screw Compressor
- Gas Management System / Oil Remover System
- Pure Gas Buffer
- Impure Gas Adsorber
- Control Cabinet and SCADA System