Calculation and thermodynamic analysis on liquefaction processes of natural gas with expanders

In order to compare the exergy loss and energy consumption of different liquefaction processes, the calculations of the energy consumption under different mol fractions of methane in refrigerants were performed. The result shows that the energy consumption is smallest and the liquefied process can be optimized when the mol fraction of methane is 50%. Then two processes for liquefied natural gas production were evaluated, including a single-stage expander nitrogen-methane refrigerant with another propane refrigeration cycle (1st project) and a two-stage expander nitrogen-methane refrigerant (2nd project). Steady-state simulations and calculations were conducted to ensure that each process was compared on an identical basis. The full energy and exergy analysis including feed-in gas and refrigerant stream shows that the 1st project has lower exergy loss and less energy consumption.