Dynamic Analysis and Development of Process Control System with Logics for Compressor and Oil Removal System of He Plant

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 ( cryogenic temperature). To avoid high heating and to reduce the work requirement in the compression, oil of heavy molecule, which has high specific heat is mixed with helium before compression. But for refrigeration, it is necessary to cool He gas to about room temperature and separate the oil from the mixture. For removing the oil, oil removing components and other instrumentations needed. This whole system is called as Compressor and Oil Removal System (CORS).

This includes one important warm gas (helium) management system(WGM) which includes 3 pressure control valves for maintaing the operating pressure values. these 3 valves have to be operated in a controlled manner with a proper control sequence and to reach the stable situation .In these situations, pressure, temperature, flow rate, speed of compressor, efficiency of different components and power requirements of compressor will change very fast. It is necessary to the analysis the dynamic behavior of these parameters and existing CORS system components for the evolution and finding an optimum operational sequence(Discharge pressure 14 bar and Suction pressure 1.05 bar) of control valves with system mass flow rate is 70g/s to reach to a steady state situation which is simulated and analyzed dynamically by Aspen HYSYS software. This knowledge can be utilized for optimization of performance of existing CORS plant and enables to make more efficient operation. The work involved Design of a control system and development of control logic for nominal and off-nominal operational scenarios of Helium plant, Project include the process design, control system architecture, process flow chart (PFC) and control algorithm for helium plant.