Advanced exergy and exergoeconomic analysis of a multi-stage Rankine cycle system combined with hydrate energy storage recovering LNG cold energy

Abstract

In recent years, liquified natural gas (LNG) cold energy utilization technology has been widely investigated due to the increasing global use of LNG. The LNG stored at −162 °C needs to be regasified. To efficiently recover the large amount of cold energy released during the regasification process of LNG with lower investment, a multi-stage Rankine cycle system combined with hydrate energy storage and seawater ice-making cycle was carried out, and the advanced exergy and exergoeconomic analysis was conducted in this paper. The Aspen HYSYS V11 was selected to establish the LNG cold energy recovery process. The result of exergy analysis shows that the exergy destruction rate and exergy efficiency of the total system are 1662.655 kW and 41.149 %, respectively. For conventional analysis results, the burner gives the highest exergy destruction and total cost rate, while considering the result of advanced exergy and exergoeconomic analysis, the condenser 2 gives the highest avoidable exergy destruction, and the turbine 1 gives the highest avoidable total cost rate. In addition, 26.49 % of exergy destruction, 31.6 % of exergy destruction cost rate and 6.59 % of investment cost rate are avoidable, which indicated the optimization potential of the proposed system.