Advanced natural gas liquefaction process on LNG supply chain with liquid air: From design to thermodynamic and techno-economic analyses

This study proposes an advanced natural gas liquefaction process by applying liquid air to the propane pre-cooled mixed refrigerant (C3MR) process. Being the most efficient process, the C3MR process has the largest market share in the natural gas liquefaction industry. The proposed concept involves recovering cold energy released by liquefied natural gas (LNG) by introducing liquid air as the recovery medium, in which the natural gas liquefaction and LNG regasification stages are integrated. The proposed C3MR-liquid air (C3MR-LA) process was optimized using a genetic algorithm for four different process configurations. The best design produced 737.41 kJ/kg-LNG for natural gas liquefaction, which is 26.4% less than in the optimized commercial C3MR process. In addition, a techno-economic analysis is conducted, and the results show that 25.1% of expenses could be saved through energy recovery by applying liquid air. By including liquid air in the LNG supply chain, the developed process achieves superior performance from both the energy and economic perspectives. A thermodynamic analysis shows that the newly proposed process can reduce exergy waste by 21.0% over the entire LNG supply chain compared to existing technology. Overall, this study proposes an attractive process model for natural gas liquefaction through cold energy recovery, which is expected to contribute to increasing the sustainability of the LNG industry.