Investigation of improvement potential of Modified Single Mixed Refrigerant (MSMR) LNG process in terms of avoidable and unavoidable exergy destruction

Abstract

Keeping in view recent energy challenges, natural gas (NG) and other associated fuels such as liquefied petroleum gas (LPG) have been taken into account being clean sources of energy as compared with oil and coal. Due to economic infeasibility of NG transportation through pipelines, liquefied natural gas (LNG) is considered as a promising eco-friendly candidate to transport natural gas to remote locations around the globe. However, the NG liquefaction is an energy and cost-intensive process mainly because of large amount of energy consumption by compression units taking part in liquefaction process. In this study, newly developed modified single mixed refrigerant (MSMR) process was utilized to liquefy NG which is specially targeted for offshore application. To examine the real potential for improvements in MSMR process, the sources of irreversibilities are identified using advanced exergy analysis (AEA). Conventional exergy analysis (CEA) on MSMR LNG process was applied to evaluate the exergy destruction through involved components. Keeping in view to compute potential of improvement in the whole process, destruction of exergy of the process was divided into unavoidable and avoidable sections. Unavoidable part of total exergy destruction was observed only 42% which was less than avoidable portion leading the analyzer to gauge the real potential of improvement. Composite curves analysis was also carried through to analyze the heat transfer efficiency and overall performance of cryogenic heat exchangers involved in the MSMR process.