Thermodynamic analysis and system simulation of an “optimized cascade” LNG process

Since 1960, LNG technology has been constantly evolving, and it has become an active subject of research in industrial and academic fields. The improvements in the natural gas liquefaction and shipping processes have led to a decrease in the total cost of the delivered LNG of approximately 30% in the last 20 years, mostly as a consequence of technological advancements. In this work a variant of the ConocoPhillips process has been modelled and simulated by a Process Software Simulator, CAMEL-Pro. The design data were extracted from publicly available information. The system has been reconfigured and it is referred here to as “Actual Optimized Cascade Process” (A-OCP). The simulation is conducted per unit mass of natural gas and the refrigerants used are propane, ethane, methane, nitrogen and seawater. The simulation shows that 67% of the natural gas intake is liquefied, with a Coefficient of Performance COP=0.14. In addition, an Exergy Analysis was carried out, which demonstrated an overall exergy efficiency of 16%. Finally, a Pinch Technology based heat transfer analysis was performed, and a detailed inspection of the Composite Curves led to the configuration of a Heat Exchanger Network to cover the cooling needs with a system pinch ∆Tpp=8.3 K.