Simulation of the Production of Liquefied Natural Gas (LNG) from Flare Gas Using Aspen HYSYS: A Critical Review

Abstract

Routine gas flaring remains both an environmental burden and a loss of potentially marketable energy. This review critically evaluates the use of Aspen HYSYS and related process-simulation approaches for converting flare gas to liquefied natural gas (LNG), with emphasis on the complete process chain rather than on isolated recovery units. A structured literature review was organized around five technical themes: flare-gas feed variability and pretreatment, thermodynamic-model selection, liquefaction-cycle configuration, energy and exergy performance, and techno-economic/environmental assessment. The evidence shows that the technical feasibility of flare-gas liquefaction depends strongly on removal of CO₂, H₂S, water and heavy hydrocarbons before cryogenic cooling; appropriate representation of hydrocarbon phase behavior, commonly with the Peng–Robinson equation of state; and careful matching of refrigerant composition, pressure levels and heat-exchanger temperature profiles. Single mixed-refrigerant/PRICO configurations are attractive for small-scale applications because of their relative simplicity, whereas cascade and pre-cooled mixed-refrigerant systems can offer improved thermodynamic performance at the cost of greater process complexity. Across the reviewed literature, compressor power and cryogenic heat-exchanger performance emerge as dominant optimization targets. However, direct studies integrating real flare-gas variability, complete pretreatment, LNG liquefaction, dynamic operation, exergy analysis, emissions quantification and economic optimization in one Aspen HYSYS framework remain limited. The review therefore proposes a research framework in which feed characterization, pretreatment, liquefaction, nitrogen/heavy-component management, energy optimization, dynamic validation and sustainability assessment are treated as an integrated problem. This synthesis clarifies the specific contribution that future Aspen HYSYS studies should make beyond simply reproducing conventional natural-gas liquefaction flow sheets.