Design and Analysis for Adoption of Oil Injected Air Screw Compressor and Oil Removal System for Compression of Helium Gas

Abstract

The Helium Refrigerator/Liquefier (HRL) plant needs compression of helium gas, which is then, cooled and expanded to produce liquid helium at 4.5 K. Considering the high volumetric ow rate and medium pressure requirements, oil injected screw compressors are used for helium compression process in the helium plant. There are heat exchangers, bulk oil separator tank, oil recirculation pumps, oil vapor coalescers and oil adsorber beds, filters, valves and other instrumentations which together is known as Compressor and Oil Removal System (CORS). Most of screw compressors are using air as working uid and oil removal system is designed for the same. Helium is having different properties than air specially, the specific heat ratio is very high. Also as helium is costly gas, its leakage from compressor should also be very low. Considering these requirements, appropriate and simpler modifications are worked out. Thus, this project involves how an oil injected air screw compressor and oil removal system can be converted to helium compressor and oil removal system. Volumetric efficiency and power requirements for helium and air compressions are calculated and compared using mathematical modeling. A closed loop piping system with valves is designed for conversion of open loop air CORS to helium CORS. In oil removal system, adsorber bed is designed for helium and air application. This thesis presents the details of these analysis and results.