Calculations and exergy analysis on several kinds of liquefaction processes of natural gas

By using Advanced System for Process Engineering (ASPEN) and Visual Fortran software, three typical processes for liquefied natural gas (LNG) production were evaluated. These include a single-stage expander nitrogen-methane refrigerant with another propane refrigeration cycle (Project I) and two kinds of two-stage expander nitrogen-methane refrigerant (Project II) and another two-stage parallel expander nitrogen-methane refrigerant (Project III). Steady-state simulations and calculations were undertaken to ensure that each process was compared on an identical basis. The full energy and exergy analysis including feed gas and refrigerant stream show that Project I has lower exergy loss and the less energy consumption than the latter two projects. The valid ways to calculate and optimize LNG process were presented.