Optimization of a novel liquefaction process based on Joule-Thomson cycle utilizing high-pressure natural gas exergy by genetic algorithm

A novel liquefaction process based on Joule-Thomson cycle utilizing high-pressure natural gas exergy is specifically proposed and presented in this paper. Thermodynamic and economic optimization of the novel process are performed with the genetic algorithm (GA) in Microsoft Excel VBA connecting Aspen HYSYS. Five different objective functions are selected: minimization of specific energy consumption (SEC), total cost investment (TCI), specific operation cost (SOPEX), total annualized cost (TAC) and maximization of exergy efficiency. The specific energy consumption objective function is equivalent to exergy efficiency, SOPEX, TAC objective functions. Compared to TCI objective function, the other four objective functions can result in an about 49% reduction of SEC, an about 99% increase of exergy efficiency, an about 2% reduction of SOPEX and an about 2.8% reduction of TAC, but an about 95% increase of TCI. The results show that any of SEC, exergy efficiency, SOPEX and TCI objective functions is more suitable for the optimization of this process. Finally, the exergy analysis of each component is given. It can be found that compressors and water coolers produce the highest exergy losses for the equivalent objective functions.