Exploring efficiency: an in-depth analysis of the energy, exergy, and sensitivity in four traditional liquefied natural gas processes

This study delves into the comprehensive analysis of four conventional mixed refrigerant liquefaction processes, namely C3MR-Linde, C3MR-APCI, SMR-Linde, and SMR-APCI, emphasizing energy and exergy perspectives. According to the energy analysis, C3MR-Linde demonstrates a lower energy consumption than the other systems, at 0.271 kWh kg⁻¹ liquefied natural gas, while SMR-Air Products achieves the highest coefficient of performance (COP) at 2.67 kWh kg⁻¹. The exergy analysis provides insights into the exergy efficiency and destruction of components, highlighting the C3MR-Linde process as the most exergy-efficient process, attaining 47.55%. Notably, compressors are identified as the primary sources of exergy destruction, accounting for 52.11%, 52.51%, and 45.39% of the overall cycle exergy destruction in the C3MR-APCI, C3MR-Linde, and SMR-APCI cycles, respectively. Furthermore, this study investigates how certain operational factors affect the COP, specific energy consumption (SEC), and exergy indices. It is observed that each cycle exhibits an optimal pressure drop in the expansion valves, with deviations resulting in a decreased COP and increased SEC. Additionally, changes in the refrigerant molar flow rates demonstrate an inverse relationship between the exergy efficiency and COP, with the SEC being notably more sensitive to such variations than the COP within the studied parameters.