| 초록 |
During the loading of LNG, excessive boil-off gas (BOG) is unavoidable due to the large temperature difference between the LNG and a tank, which causes a pressure change. Therefore, it is necessary to decrease the temperature of the tank before loading the LNG, which is known as a cool-down process. During the cool-down process, the tank temperature is gradually reduced by the LNG spray and it generates BOG. For safe operation, vent gas is released from the tank to control the pressure. Hence, in this work, a model predicted control system that can regulate the tank pressure and temperature was formulated and applied to the cool-down process. First, a mathematical model was developed. Second, a reduced-order model was proposed using N4SID algorithm. The developed model was then utilized in the MPC scheme to control the pressure and temperature of the tank. As a result, the MPC system was able to drive the pressure and temperature to set-point while obtaining optimal input sequences. |
