PLC를 이용한 LNG 공정 제어 밸브의 PID 제어기 구현과 성능에 관한 연구

Abstract

Recently, LNG(Liquefied Natural Gas) has been receiving spotlight as an eco-friendly energy source. This is because there is little pollution than conventional petroleum fuel. To use LNG as fuel, it is stored and transported using a specialized cryogenic tank. During this process, the LNG naturally evaporates as the temperature of the LNG tank increases due to the temperature difference between the inside and the outside the tank. This evaporated material is called BOG (Boil Off Gas). Over time, it is likely that the tank will be damaged or even, in worst cases, explode if the volume of the BOG increases and exceeds the designed pressure of the tank. Therefore, the control of the temperature and the pressure of the tank is required to control the volume of the BOG. In this paper, we identified various control techniques, types of PLC(Programmable Logic Controller)s, and theories for programming PLCs. Also, the process simulator was used to simulate the LNG tank process and to control the temperature and pressure of the LNG tank. And the PID(Proportional-Integral-Derivative) controller of process simulator and the PID controller of the PLC are applied to compare the results and the effectiveness of the PID controller.