Dynamic Modeling and Simulation for LNG Value Chain
摘要
Natural gas is widely used as heating fuel as well as a raw material for various chemical processes and its usage has been continuously increasing due to its cleanness and economic feasibility. However, the use of natural gas is limited by its gaseous state which brings significant challenges for its transport to distant markets. The LNG (Liquefied Natural Gas) which reduces the volume of natural gas to 1/600 makes it possible to transport natural gas to remote regions. At LNG production sites, such as in the Middle East, natural gas is liquefied and then transported to the demand region by LNG carrier ship. LNG in a carrier ship is usually transferred onshore to a LNG receiving terminal via an LNG unloading process.\nThis thesis addresses the dynamic modeling and simulation for LNG value chain and it contains two main processes: one is the liquefaction process which occurred in natural gas liquefaction plant and the other is LNG unloading process in LNG receiving terminal. These two processes occupy the main parts in the whole in LNG value chain and are worth to be studied in depth. \nThis thesis has five main parts. First, we developed a plantwide steady-state model for natural gas liquefaction plant which covers from pretreatment to post-treatment section. The constructed model was tested with model validation. Secondly, a dynamic model was developed for natural gas liquefaction plant based on the steady-state model. The developed dynamic model was validated with steady-state data and set point tracking. We also suggest a new control structure for MCHE (Main Cryogenic Heat Exchanger) operation. The third part of the thesis, we proposed a dynamic modeling methodology for plate-fin heat exchanger when using commercial simulator. We have achieved this goal by adopting optimization technique to parameter estimation. Turning our concerns to LNG receiving terminal, the LNG unloading process was considered at the remaining parts. At fourth part, the dynamic simulation w