Thermodynamic Analysis of a Baseload LNG Plant

Baseload natural gas liquefaction plant technology is currently dominated by the propane pre-cooled multicomponent refrigerant cycle licensed by Air Products and Chemicals Inc (APCI). In this paper, APCI's LNG process is described and key performance indicators are presented based on process simulation and rigorous thermodynamic analysis. Results for a plant producing 2.4 million tonnes of LNG per annum show that approximately 8% of the incoming natural gas is consumed to provide the shaft power to drive the refrigerant compressors and cooling water pumps. The overall compressor power consumption is 13.6 kW per t/d, of LNG. The pre-cooling and multicomponent refrigerant cycles operate at 34.3% and 58.3% thermodynamic efficiency respectively, with an overall efficiency of 40.6%. The contributions of individual heat exchangers, Joule-Thompson valves arid compressors to efficiency loss have been identified using exergy analysis.