Dynamic modeling and predictive control of boil-offgas generation during LNG loading

초록

During liquefied natural gas (LNG) loading, excessive boil-offgas (BOG) is generated due to the temperature difference between the LNG and a tank at room temperature. While one way to deal with this challenge is to gradually reduce the tank temperature via an LNG, this cool-down process may also produce excessive BOG, if not properly handled, leading to a sudden pressure change inside the tank. To this end, a model predictive control (MPC) system was formulated in this work to simultaneously regulate the pressure and temperature of the tank by manipulating the vapor outlet flow rate and the amount of LNG spray injected during the cool-down process. Specifically, a high-fidelity model of cool-down process was developed and simplified to a reduced-order model (ROM). Then, the ROM was incorporated into the developed MPC scheme which successfully computed an input profile to drive the pressure and tank temperature to target values. (C) 2022 Elsevier Ltd. All rights reserved.

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