Closed-Loop Self-Cooling Recuperative N2 Expander Cycle for the Energy Efficient and Ecological Natural Gas Liquefaction Process

Abstract

Liquefied natural gas (LNG) has attracted global attention as a more environmentally friendly energy source when compared to other fossil fuels. The nitrogen (N2) expander liquefaction is the most green and safe process among the different types of commercial natural gas liquefaction processes, but its relatively low energy efficiency is a major issue. In this study, an innovative closed-loop self-cooling recuperation technology was proposed to reduce the exergy losses of the N2 expander LNG process. The LNG process with the implementation of the proposed technology was modeled using a commercial process simulation tool, ASPEN HYSYS v9. Subsequently, a modified coordinate descent optimization algorithm was employed to achieve maximum potential benefits of the proposed technology. The energy efficiency of the proposed LNG process was further improved by energy recovery from end flash gas and high-pressure natural gas feed. Finally, the energy efficiency of the proposed closed-loop self-cooling recuperative...