Exergy, Exergoeconomic, Exergoenvironmental Analysis and Working Fluid Picking of an Integrated Liquefied Natural Gas Cold Energy Utilization System Consisting of an Organic Rankine Cycle and Two-Stage Turbine Organic Flash Cycle

A novel integrated system is suggested herein to recover liquefied natural gas (LNG) cold energy more reasonably and effectively, containing an organic Rankine cycle (ORC), a two-stage turbine organic flash cycle (TTOFC), and an LNG expansion cycle. R134a-R32, R134a-Propylene, R152a-Propylene, and R152a-R32 are picked as the working fluid combinations for the system. A comprehensive study, including the net outpower power, exergy, exergoeconomic, and exergoenvironmental analysis, is conducted. The effects of the turbine 1 inlet temperature, the ORC working fluid mass flow in the heat exchanger 3, the pump 5 outlet pressure, and the inlet pressure for the flash tank in the TTOFC on the performance of the above three criteria are presented. The NSGA-II method is used for three-objective optimization and another design with ORC and single-stage turbine organic flash cycle is set to compare with the new combined cooling, heating, and power system. The results show that R134a-R32 is the best combination. In the R134a-R32 combination, the total capital cost is 25.64 $ h(-1), and the total environmental impact is 53.75 mPts h(-1).

Automated summary

A novel integrated system combining an organic Rankine cycle (ORC), a two-stage turbine organic flash cycle (TTOFC), and an LNG expansion cycle is proposed to recover LNG cold energy more effectively. Four different working fluid combinations are studied for the system. The effects of various parameters on the performance of three different criteria are analyzed, and optimization is conducted using the NSGA-II method. The results show that R134a-R32 is the best combination with the lowest total capital cost and environmental impact.