Exergy analysis of an ethylene refrigeration cycle integrated with a NGL recovery process for a large LNG train

Abstract

The natural gas liquefaction process consists of a sequence of refrigeration cycles that consumes a considerable amount of energy. The separation of natural gas (NG) from the natural gas liquids (NGL) is considered to be one of the significant parts in the liquefaction of natural gas, as this will influence the LNG product quality. The integration of NGL section with the liquefaction process is one of the fundamental ways to improve the efficiency of the process and provide economic benefit from operating and capital cost perspectives. In this extended abstract, two different configurations of NGL section integrated with the ethylene refrigeration cycle for the Cascade LNG plant—processing 5 million tonnes per annum (MTPA)—are proposed. The objectives of the proposed concepts are to meet the LNG higher heating value (HHV) specification and to achieve minimum power consumption for the refrigeration cycle. Exergy analysis is used as a thermodynamic tool to evaluate the efficiency of the process. The process was simulated using Aspen HYSYS and the results of the proposed configurations are presented and analysed. The proposed configurations can be used to produce LNG and NGL with minimum energy consumption.