C3MR LNG process design: Novel approach to optimization for feedstock variability and multi-criteria analysis including economics, safety and environmental impact

The global trade of liquefied natural gas (LNG) has achieved a substantial increase in the past decades. Consequently, the technology for natural gas liquefaction has received a considerable attention from the academic community. However, the effect of different compositions of natural gas on the technology has not been thoroughly studied yet. This paper studies twelve different compositions of natural gas and their impact on the propane-precooled mixed-refrigerant (C3MR) LNG process and its products. Considering each feedstock, the specific energy consumption of the C3MR process was optimized. The optimization results declared a 14–30 % possible decrease in the specific energy consumption while they were significantly affected by the composition of natural gas. Moreover, the study unveiled that the LNG quality criteria are not met when processing natural gas with a high content of nitrogen. Hence, eight alternative designs of the C3MR process were proposed to lower the process carbon footprint, to improve the economic feasibility of the process, and to meet the LNG quality criteria. The alternatives were subjected to a thorough economic, environmental, and safety evaluation. Finally, a multi-criteria decision analysis employing the analytical hierarchy process was carried out to select the most suitable design alternative for each type of feedstock. Overall, this study bridges the gaps present in the published LNG studies and provides a comprehensive contribution to the topic of optimization and multi-criteria decision analysis.